RFC 8022

A YANG Data Model for Routing Management

๐Ÿ“… published November 2016, from ietf

A YANG Data Model for Routing Management โœจ

Part 1 of 11 ๐ŸŽ€

Okay, so the title block is giving "official paperwork" ๐Ÿ“„, but here's the tea. This is an IETF document (RFC 8022, published November 2016), written by L. Lhotka from CZ.NIC and A. Lindem from Cisco Systems ๐Ÿงš. It's in the Standards Track category ๐Ÿ’…, and its ISSN is 2070-1721. The header doesn't have an Obsoletes or Updates line, so it doesn't list anything it replaces or changes.

Abstract

Okay so this doc specs out three YANG modules and one submodule ๐ŸŒธ. Together they make up the core routing data model, which is basically a framework for configuring and managing a routing subsystem. Other modules are expected to augment it later with data models for control-plane protocols, route filters, and other stuff. The core model gives everyone the common building blocks: routes, Routing Information Bases (RIBs), and control-plane protocols ๐Ÿ”ฅ.

Status of This Memo

This is an Internet Standards Track document ๐Ÿ‘‘.

It's a product of the Internet Engineering Task Force (IETF) and represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). If you want more on Internet Standards, check out Section 2 of RFC 7841 ๐Ÿซถ.

For the current status, any errata, and how to send feedback, go to http://www.rfc-editor.org/info/rfc8022 ๐Ÿฆ‹.

Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved ๐Ÿ’œ.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they were in effect on the date of publication. Please read these carefully, bestie, because they spell out your rights and restrictions for this document ๐Ÿ“œ. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions, and they come without warranty as described in the Simplified BSD License โญ.

Table of Contents

1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
2.  Terminology and Notation  . . . . . . . . . . . . . . . . . .   3
  2.1.  Glossary of New Terms . . . . . . . . . . . . . . . . . .   4
  2.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   5
  2.3.  Prefixes in Data Node Names . . . . . . . . . . . . . . .   5
3.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   6
4.  The Design of the Core Routing Data Model . . . . . . . . . .   6
  4.1.  System-Controlled and User-Controlled List Entries  . . .   8
5.  Basic Building Blocks . . . . . . . . . . . . . . . . . . . .   9
  5.1.  Route . . . . . . . . . . . . . . . . . . . . . . . . . .   9
  5.2.  Routing Information Base (RIB)  . . . . . . . . . . . . .   9
  5.3.  Control-Plane Protocol  . . . . . . . . . . . . . . . . .  10
    5.3.1.  Routing Pseudo-Protocols  . . . . . . . . . . . . . .  10
    5.3.2.  Defining New Control-Plane Protocols  . . . . . . . .  11
  5.4.  Parameters of IPv6 Router Advertisements  . . . . . . . .  12
6.  Interactions with Other YANG Modules  . . . . . . . . . . . .  13
  6.1.  Module "ietf-interfaces"  . . . . . . . . . . . . . . . .  13
  6.2.  Module "ietf-ip"  . . . . . . . . . . . . . . . . . . . .  13
7.  Routing Management YANG Module  . . . . . . . . . . . . . . .  14
8.  IPv4 Unicast Routing Management YANG Module . . . . . . . . .  26
9.  IPv6 Unicast Routing Management YANG Module . . . . . . . . .  32
  9.1.  IPv6 Router Advertisements Submodule  . . . . . . . . . .  37
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  47
11. Security Considerations . . . . . . . . . . . . . . . . . . .  48
12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  49
  12.1.  Normative References . . . . . . . . . . . . . . . . . .  49
  12.2.  Informative References . . . . . . . . . . . . . . . . .  50
Appendix A.  The Complete Data Trees  . . . . . . . . . . . . . .  51
  A.1.  Configuration Data  . . . . . . . . . . . . . . . . . . .  51
  A.2.  State Data  . . . . . . . . . . . . . . . . . . . . . . .  52
Appendix B.  Minimum Implementation . . . . . . . . . . . . . . .  53
Appendix C.  Example: Adding a New Control-Plane Protocol . . . .  54
Appendix D.  Data Tree Example  . . . . . . . . . . . . . . . . .  56
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  64
Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  64

1. Introduction ๐ŸŒˆ

This doc specs out the following YANG modules:

  • The ietf-routing module gives you the generic components of a routing data model ๐Ÿ’–.
  • The ietf-ipv4-unicast-routing module augments ietf-routing with extra data that's specific to IPv4 unicast ๐Ÿ“.
  • The ietf-ipv6-unicast-routing module augments ietf-routing with extra data that's specific to IPv6 unicast. Its submodule, ietf-ipv6-router-advertisements, also augments the ietf-interfaces [RFC7223] and ietf-ip [RFC7277] modules with IPv6 router configuration variables that [RFC4861] needs ๐Ÿงš.

Together these three modules are the so-called core routing data model ๐Ÿ‘‘. It's meant to be the base for future data model work covering more sophisticated routing systems. You can use these three modules directly on simple IP devices with static routing (see Appendix B), but their real purpose is to be essential building blocks for more complicated data models. That means multiple control-plane protocols, multicast routing, extra address families, and advanced stuff like route filtering or policy routing ๐Ÿฆ‹. So yeah, the plan is for lots of IETF working groups to augment the core routing data model with their own modules ๐Ÿ”ฅ.

2. Terminology and Notation โœจ

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] ๐Ÿ’….

These terms are defined in [RFC6241]:

  • client
  • message
  • protocol operation
  • server

These terms are defined in [RFC7950]:

  • action
  • augment
  • configuration data
  • container
  • container with presence
  • data model
  • data node
  • feature
  • leaf
  • list
  • mandatory node
  • module
  • schema tree
  • state data
  • RPC (Remote Procedure Call) operation

2.1. Glossary of New Terms ๐Ÿ’œ

  • core routing data model: a YANG data model made up of the ietf-routing, ietf-ipv4-unicast-routing, and ietf-ipv6-unicast-routing modules.
  • direct route: a route to a directly connected network.
  • Routing Information Base (RIB): an object that holds a list of routes plus other info. See Section 5.2 for details ๐ŸŽ€.
  • system-controlled entry: an entry of a list in state data (config false) that the system creates on its own, independent of anything explicitly configured. See Section 4.1 for details โญ.
  • user-controlled entry: an entry of a list in state data (config false) that gets created and deleted as a direct result of certain configuration changes. See Section 4.1 for details ๐Ÿซถ.

2.2. Tree Diagrams ๐Ÿ“

A simplified graphical view of the complete data tree is in Appendix A, and similar diagrams for its various subtrees show up in the main text ๐Ÿงš. Here's how to read them:

  • Brackets [ and ] enclose list keys.
  • Curly braces { and } contain the names of optional features that make the corresponding node conditional.
  • Abbreviations before data node names: rw means configuration (read-write), ro means state data (read-only), -x means RPC operations or actions, and -n means notifications.
  • Symbols after data node names: ? means an optional node, ! means a container with presence, and * denotes a list or leaf-list.
  • Parentheses enclose choice and case nodes, and case nodes are also marked with a colon (:).
  • Ellipsis (...) stands for the contents of subtrees that aren't shown.

2.3. Prefixes in Data Node Names ๐ŸŒธ

In this doc, names of data nodes, actions, and other data model objects are often used without a prefix, as long as the context makes it clear which YANG module each name is defined in. Otherwise, names get the standard prefix tied to their YANG module, as shown in Table 1 ๐Ÿ’–.

         +--------+---------------------------+-----------+
         | Prefix | YANG module               | Reference |
         +--------+---------------------------+-----------+
         | if     | ietf-interfaces           | [RFC7223] |
         | ip     | ietf-ip                   | [RFC7277] |
         | rt     | ietf-routing              | Section 7 |
         | v4ur   | ietf-ipv4-unicast-routing | Section 8 |
         | v6ur   | ietf-ipv6-unicast-routing | Section 9 |
         | yang   | ietf-yang-types           | [RFC6991] |
         | inet   | ietf-inet-types           | [RFC6991] |
         +--------+---------------------------+-----------+

          Table 1: Prefixes and Corresponding YANG Modules

3. Objectives ๐Ÿ”ฅ

The initial design of the core routing data model was driven by these objectives, and honestly they're iconic ๐Ÿ‘‘:

  • The data model should be suitable for the common address families (in particular, IPv4 and IPv6) and for unicast and multicast routing, as well as Multiprotocol Label Switching (MPLS) ๐Ÿฆ‹.
  • A simple IP routing system, like one that only uses static routing, should be configurable in a simple way, ideally without needing to develop any additional YANG modules ๐ŸŽ€.
  • On the other hand, the core routing framework has to allow for complicated implementations. That means multiple Routing Information Bases (RIBs), multiple control-plane protocols, and controlled redistributions of routing information ๐Ÿ’….
  • Device vendors are going to want to map data models built on this generic framework to their own proprietary data models and configuration interfaces. So the framework should be flexible enough to make that easy and to accommodate data models with different logic ๐ŸŒˆ.

4. The Design of the Core Routing Data Model โœจ

okay so the core routing data model is made of three YANG modules and one submodule ๐ŸŽ€ The first one, "ietf-routing", holds the generic stuff every routing system needs ๐Ÿงš The other two, "ietf-ipv4-unicast-routing" and "ietf-ipv6-unicast-routing", augment "ietf-routing" with the extra data nodes needed for IPv4 and IPv6 unicast routing, respectively. The "ietf-ipv6-unicast-routing" module also has a submodule, "ietf-ipv6-router-advertisements", which augments the "ietf-interfaces" [RFC7223] and "ietf-ip" [RFC7277] modules with configuration variables for IPv6 router advertisements, as required by [RFC4861] ๐Ÿ’…

Figures 1 and 2 give you abridged views of the configuration and state data hierarchies, and Appendix A has the complete data trees ๐ŸŒธ

+--rw routing
   +--rw router-id?
   +--rw control-plane-protocols
   |  +--rw control-plane-protocol* [type name]
   |     +--rw type
   |     +--rw name
   |     +--rw description?
   |     +--rw static-routes
   |        +--rw v6ur:ipv6
   |        |     ...
   |        +--rw v4ur:ipv4
   |              ...
   +--rw ribs
      +--rw rib* [name]
         +--rw name
         +--rw address-family?
         +--rw description?

Figure 1: Configuration Data Hierarchy

+--ro routing-state
   +--ro router-id?
   +--ro interfaces
   |  +--ro interface*
   +--ro control-plane-protocols
   |  +--ro control-plane-protocol* [type name]
   |     +--ro type
   |     +--ro name
   +--ro ribs
      +--ro rib* [name]
         +--ro name
         +--ro address-family
         +--ro default-rib?
         +--ro routes
         |  +--ro route*
         |        ...

Figure 2: State Data Hierarchy

As you can see from Figures 1 and 2, the core routing data model brings in a few generic building blocks for a routing framework: routes, RIBs containing lists of routes, and control-plane protocols ๐Ÿฆ‹ Section 5 breaks these down in more detail.

4.1. System-Controlled and User-Controlled List Entries ๐ŸŒˆ

The core routing data model defines several lists in the schema tree, like "rib", that have to be populated with at least one entry on any properly functioning device. Extra entries can be configured by a client ๐Ÿ“

On the server side, the required item gets created as a so-called system-controlled entry in state data, meaning inside the "routing-state" container ๐Ÿค–

Check Appendix D for an example: the "/routing-state/ribs/rib" list has two system-controlled entries, named "ipv4-master" and "ipv6-master" ๐Ÿ‘‘

A client can also add entries to the configuration, e.g., via the NETCONF protocol. These are so-called user-controlled entries ๐Ÿซถ If the server accepts a configured user-controlled entry, that entry also shows up in the state data version of the list.

Corresponding entries in both versions of the list (state data and configuration) have the same value of the list key ๐Ÿ’œ

A client can also give supplemental configuration to system-controlled entries ๐Ÿงš To do that, it creates a new entry in the configuration with the contents it wants. To bind this entry to the matching entry in the state data list, the key of the configuration entry has to be set to the same value as the key of the state entry.

Deleting a user-controlled entry from the configuration list removes the matching entry in the state data list too ๐Ÿ’€ But it's different for system-controlled entries: if one gets deleted from the configuration list, only the extra configuration specified in that entry is removed, and the corresponding state data entry stays put in the list ๐Ÿ™ˆ

5. Basic Building Blocks ๐Ÿง

This section is all about the essential components of the core routing data model. Let's get into it ๐Ÿ’…

5.1. Route ๐Ÿ›ฃ๏ธ

Routes are the basic elements of information in a routing system. The core routing data model defines only this minimal set of route attributes:

  • "destination-prefix": address prefix specifying the set of destination addresses for which the route may be used. This attribute is mandatory.
  • "route-preference": an integer value (also known as administrative distance) used for picking a preferred route among routes with the same destination prefix. A lower value means a more preferred route.
  • "next-hop": determines the outgoing interface and/or next-hop address(es), or a special operation to be performed with a packet.

Routes are mostly state data that show up as entries of RIBs (Section 5.2), but they can also live in configuration data, for example as manually configured static routes. In that case, the configurable route attributes are generally a subset of the attributes defined for RIB routes ๐ŸŽ€

5.2. Routing Information Base (RIB) ๐ŸŒธ

Every implementation of the core routing data model manages one or more Routing Information Bases (RIBs) ๐Ÿ“š A RIB is a list of routes complemented with administrative data. Each RIB contains only routes of one address family, and an address family is represented by an identity derived from the "rt:address-family" base identity.

In the core routing data model, RIBs are state data, represented as entries of the list "/routing-state/ribs/rib". Their contents are controlled and manipulated by control-plane protocol operations, which may result in route additions, removals, and modifications. This also includes manipulations via the "static" and/or "direct" pseudo-protocols (see Section 5.3.1) ๐Ÿฆ‹

For every supported address family, exactly one RIB MUST be marked as the so-called default RIB, which is where control-plane protocols put their routes by default ๐Ÿซถ

Simple router implementations that don't advertise the feature "multiple-ribs" will typically create one system-controlled RIB per supported address family and mark it as the default RIB ๐Ÿฐ

More-complex router implementations that advertise the "multiple-ribs" feature support multiple RIBs per address family, which can be used for policy routing and other purposes ๐Ÿง 

The following action (see Section 7.15 of [RFC7950]) is defined for the "rib" list:

  • active-route -- return the active RIB route for the destination address that is specified as the action's input parameter.

5.3. Control-Plane Protocol ๐Ÿš€

The core routing data model gives you an open-ended framework for defining multiple control-plane protocol instances, e.g., for Layer 3 routing protocols ๐ŸŒˆ Each control-plane protocol instance MUST be assigned a type, which is an identity derived from the "rt:control-plane-protocol" base identity. The core routing data model defines two identities for the direct and static pseudo-protocols (Section 5.3.1) ๐Ÿงš

Multiple control-plane protocol instances of the same type MAY be configured ๐Ÿ’–

5.3.1. Routing Pseudo-Protocols ๐Ÿซง

The core routing data model defines two special routing protocol types, "direct" and "static" ๐ŸŽ€ Both are really pseudo-protocols, which means they're confined to the local device and don't exchange any routing information with adjacent routers ๐Ÿ 

Every implementation of the core routing data model MUST provide exactly one instance of the "direct" pseudo-protocol type. It's the source of direct routes for all configured address families ๐Ÿ‘‘ Direct routes are normally supplied by the operating system kernel, based on the configuration of network interface addresses (see Section 6.2) ๐Ÿฃ

A pseudo-protocol of the type "static" lets you specify routes manually ๐Ÿ“ It MAY be configured in zero or multiple instances, although a typical configuration will have exactly one instance ๐Ÿ’…

5.3.2. Defining New Control-Plane Protocols ๐Ÿ› ๏ธ

It's expected that future YANG modules will create data models for additional control-plane protocol types ๐Ÿ”ฎ A new module like that has to define the protocol-specific configuration and state data, and it has to plug it into the core routing framework in the following way:

  • A new identity MUST be defined for the control-plane protocol, and its base identity MUST be set to "rt:control-plane-protocol" or to an identity derived from "rt:control-plane-protocol".
  • Additional route attributes MAY be defined, preferably in one place by defining a YANG grouping. The new attributes have to be inserted by augmenting the definitions of these nodes:
/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route

and

/rt:routing-state/rt:ribs/rt:rib/rt:output/rt:route

and possibly other places in the configuration, state data, notifications, and input/output parameters of actions or RPC operations.

  • Configuration parameters and/or state data for the new protocol can be defined by augmenting the "control-plane-protocol" data node under both "/routing" and "/routing-state".

By using a "when" statement, the augmented configuration parameters and state data specific to the new protocol SHOULD be made conditional, and valid only if the value of "rt:type" or "rt:source-protocol" is equal to (or derived from) the new protocol's identity ๐Ÿง

It's also RECOMMENDED that protocol-specific data nodes be encapsulated in an appropriately named container with presence ๐Ÿ“ฆ Such a container may contain mandatory data nodes that are otherwise forbidden at the top level of an augment ๐Ÿ™Œ

The above steps are put into practice by the example YANG module for the Routing Information Protocol (RIP) in Appendix C ๐ŸŽ“

5.4. Parameters of IPv6 Router Advertisements ๐Ÿ“ก

The YANG module "ietf-ipv6-router-advertisements" (Section 9.1) is a submodule of the "ietf-ipv6-unicast-routing" module. It augments the configuration and state data of IPv6 interfaces with definitions of the following variables, as required by Section 6.2.1 of [RFC4861] ๐ŸŒŸ

  • send-advertisements
  • max-rtr-adv-interval
  • min-rtr-adv-interval
  • managed-flag
  • other-config-flag
  • link-mtu
  • reachable-time
  • retrans-timer
  • cur-hop-limit
  • default-lifetime
  • prefix-list: a list of prefixes to be advertised.

The following parameters are associated with each prefix in the list:

  • valid-lifetime
  • on-link-flag
  • preferred-lifetime
  • autonomous-flag

NOTES:

  1. The "IsRouter" flag, which is also required by [RFC4861], is implemented in the "ietf-ip" module [RFC7277] (leaf "ip:forwarding") ๐Ÿงญ
  2. The original specification [RFC4861] lets implementations decide whether the "valid-lifetime" and "preferred-lifetime" parameters stay the same in consecutive advertisements or decrement in real time. The latter behavior seems problematic ๐Ÿ˜ฌ because the values might be reset again to the (higher) configured values after a configuration is reloaded. Moreover, no implementation is known to use the decrementing behavior. So the "ietf-ipv6-router-advertisements" submodule stipulates the former behavior, with constant values ๐Ÿ”’

6. Interactions with Other YANG Modules ๐Ÿค

The semantics of the core routing data model also depend on several configuration parameters that are defined in other YANG modules ๐Ÿ’ซ

6.1. Module "ietf-interfaces" ๐Ÿ”Œ

The following boolean switch is defined in the "ietf-interfaces" YANG module [RFC7223]:

/if:interfaces/if:interface/if:enabled

If this switch is set to "false" for a network-layer interface, then all routing and forwarding functions MUST be disabled on this interface ๐Ÿšซ

6.2. Module "ietf-ip" ๐Ÿ’–

okay so the "ietf-ip" YANG module [RFC7277] gives us four boolean switches, and they are lowkey the main character of interface config โœจ ๐Ÿ’…

  • /if:interfaces/if:interface/ip:ipv4/ip:enabled
    • If this switch is set to false for a network-layer interface, then all IPv4 routing and forwarding functions MUST be disabled on this interface. ๐Ÿ™ˆ
  • /if:interfaces/if:interface/ip:ipv4/ip:forwarding
    • If this switch is set to false for a network-layer interface, then the forwarding of IPv4 datagrams through this interface MUST be disabled. However, the interface MAY participate in other IPv4 routing functions, such as routing protocols. ๐Ÿฆ‹
  • /if:interfaces/if:interface/ip:ipv6/ip:enabled
    • If this switch is set to false for a network-layer interface, then all IPv6 routing and forwarding functions MUST be disabled on this interface. ๐Ÿ’€
  • /if:interfaces/if:interface/ip:ipv6/ip:forwarding
    • If this switch is set to false for a network-layer interface, then the forwarding of IPv6 datagrams through this interface MUST be disabled. However, the interface MAY participate in other IPv6 routing functions, such as routing protocols. ๐ŸŒธ

ngl the forwarding vs enabled split is so iconic ๐Ÿ˜ญ turning forwarding off doesn't mean the interface goes totally quiet, it can still hang out in routing protocols. that's the whole vibe ๐Ÿงš

Also, the "ietf-ip" module lets you configure IPv4 and IPv6 addresses and network prefixes or masks on network-layer interfaces. Configuring these on an enabled interface MUST result in an immediate creation of the corresponding direct route. The destination prefix of that route is set from the configured IP address and network prefix/mask, and the interface is set as the outgoing interface for that route. It's giving instant gratification ๐Ÿ“๐ŸŽ€


7. Routing Management YANG Module

<CODE BEGINS> file "ietf-routing@2016-11-04.yang"

module ietf-routing {

  yang-version "1.1";

  namespace "urn:ietf:params:xml:ns:yang:ietf-routing";

  prefix "rt";

  import ietf-yang-types {
    prefix "yang";
  }

  import ietf-interfaces {
    prefix "if";
  }

  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>
     WG Chair: Lou Berger
               <mailto:lberger@labn.net>

     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>

     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>

     Editor:   Acee Lindem
               <mailto:acee@cisco.com>";

  description
    "This YANG module defines essential components for the management
     of a routing subsystem.

     Copyright (c) 2016 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119.

     This version of this YANG module is part of RFC 8022;
     see the RFC itself for full legal notices.";

  revision 2016-11-04 {
    description
      "Initial revision.";
    reference
      "RFC 8022: A YANG Data Model for Routing Management";
  }

  /* Features */

  feature multiple-ribs {
    description
      "This feature indicates that the server supports user-defined
       RIBs.

       Servers that do not advertise this feature SHOULD provide
       exactly one system-controlled RIB per supported address family
       and make it also the default RIB.  This RIB then appears as an
       entry of the list /routing-state/ribs/rib.";
  }

  feature router-id {
    description
      "This feature indicates that the server supports configuration
       of an explicit 32-bit router ID that is used by some routing
       protocols.

       Servers that do not advertise this feature set a router ID
       algorithmically, usually to one of the configured IPv4
       addresses.  However, this algorithm is implementation
       specific.";
  }

  /* Identities */

  identity address-family {
    description
      "Base identity from which identities describing address
       families are derived.";
  }

  identity ipv4 {
    base address-family;
    description
      "This identity represents IPv4 address family.";
  }

  identity ipv6 {
    base address-family;
    description
      "This identity represents IPv6 address family.";
  }

  identity control-plane-protocol {
    description
      "Base identity from which control-plane protocol identities are
       derived.";
  }

  identity routing-protocol {
    base control-plane-protocol;
    description
      "Identity from which Layer 3 routing protocol identities are

       derived.";
  }

  identity direct {
    base routing-protocol;
    description
      "Routing pseudo-protocol that provides routes to directly
       connected networks.";
  }

  identity static {
    base routing-protocol;
    description
      "Static routing pseudo-protocol.";
  }

  /* Type Definitions */

  typedef route-preference {
    type uint32;
    description
      "This type is used for route preferences.";
  }

  /* Groupings */

  grouping address-family {
    description
      "This grouping provides a leaf identifying an address
       family.";
    leaf address-family {
      type identityref {
        base address-family;
      }
      mandatory "true";
      description
        "Address family.";
    }
  }

  grouping router-id {
    description
      "This grouping provides router ID.";
    leaf router-id {
      type yang:dotted-quad;
      description
        "A 32-bit number in the form of a dotted quad that is used by
         some routing protocols identifying a router.";

      reference
        "RFC 2328: OSPF Version 2.";
    }
  }

  grouping special-next-hop {
    description
      "This grouping provides a leaf with an enumeration of special
       next hops.";
    leaf special-next-hop {
      type enumeration {
        enum blackhole {
          description
            "Silently discard the packet.";
        }
        enum unreachable {
          description
            "Discard the packet and notify the sender with an error
             message indicating that the destination host is
             unreachable.";
        }
        enum prohibit {
          description
            "Discard the packet and notify the sender with an error
             message indicating that the communication is
             administratively prohibited.";
        }
        enum receive {
          description
            "The packet will be received by the local system.";
        }
      }
      description
        "Options for special next hops.";
    }
  }

  grouping next-hop-content {
    description
      "Generic parameters of next hops in static routes.";
    choice next-hop-options {
      mandatory "true";
      description
        "Options for next hops in static routes.

         It is expected that further cases will be added through
         augments from other modules.";
      case simple-next-hop {

        description
          "This case represents a simple next hop consisting of the
           next-hop address and/or outgoing interface.

           Modules for address families MUST augment this case with a
           leaf containing a next-hop address of that address
           family.";
        leaf outgoing-interface {
          type if:interface-ref;
          description
            "Name of the outgoing interface.";
        }
      }
      case special-next-hop {
        uses special-next-hop;
      }
      case next-hop-list {
        container next-hop-list {
          description
            "Container for multiple next-hops.";
          list next-hop {
            key "index";
            description
              "An entry of a next-hop list.

               Modules for address families MUST augment this list
               with a leaf containing a next-hop address of that
               address family.";
            leaf index {
              type string;
              description
                "A user-specified identifier utilized to uniquely
                 reference the next-hop entry in the next-hop list.
                 The value of this index has no semantic meaning
                 other than for referencing the entry.";
            }
            leaf outgoing-interface {
              type if:interface-ref;
              description
                "Name of the outgoing interface.";
            }
          }
        }
      }
    }
  }
  grouping next-hop-state-content {
    description
      "Generic parameters of next hops in state data.";
    choice next-hop-options {
      mandatory "true";
      description
        "Options for next hops in state data.

         It is expected that further cases will be added through
         augments from other modules, e.g., for recursive
         next hops.";
      case simple-next-hop {
        description
          "This case represents a simple next hop consisting of the
           next-hop address and/or outgoing interface.

           Modules for address families MUST augment this case with a
           leaf containing a next-hop address of that address
           family.";
        leaf outgoing-interface {
          type if:interface-state-ref;
          description
            "Name of the outgoing interface.";
        }
      }
      case special-next-hop {
        uses special-next-hop;
      }
      case next-hop-list {
        container next-hop-list {
          description
            "Container for multiple next hops.";
          list next-hop {
            description
              "An entry of a next-hop list.

               Modules for address families MUST augment this list
               with a leaf containing a next-hop address of that
               address family.";
            leaf outgoing-interface {
              type if:interface-state-ref;
              description
                "Name of the outgoing interface.";
            }
          }
        }
      }
    }

  }

Okay bestie, we're still inside the big YANG module ๐ŸŽ€ here's the rest of it, with the state data and config sections and the closing <CODE ENDS> ๐Ÿ’…

     grouping route-metadata {
       description
         "Common route metadata.";
       leaf source-protocol {
         type identityref {
           base routing-protocol;
         }
         mandatory "true";
         description
           "Type of the routing protocol from which the route
            originated.";
       }
       leaf active {
         type empty;
         description
           "Presence of this leaf indicates that the route is preferred
            among all routes in the same RIB that have the same
            destination prefix.";
       }
       leaf last-updated {
         type yang:date-and-time;
         description
           "Time stamp of the last modification of the route.  If the
            route was never modified, it is the time when the route was
            inserted into the RIB.";
       }
     }

     /* State data */

     container routing-state {
       config "false";
       description
         "State data of the routing subsystem.";
       uses router-id {
         description
           "Global router ID.

            It may be either configured or assigned algorithmically by
            the implementation.";
       }
       container interfaces {
         description
           "Network-layer interfaces used for routing.";
         leaf-list interface {
           type if:interface-state-ref;
           description
             "Each entry is a reference to the name of a configured
              network-layer interface.";
         }
       }
       container control-plane-protocols {
         description
           "Container for the list of routing protocol instances.";
         list control-plane-protocol {
           key "type name";
           description
             "State data of a control-plane protocol instance.

              An implementation MUST provide exactly one
              system-controlled instance of the 'direct'
              pseudo-protocol.  Instances of other control-plane
              protocols MAY be created by configuration.";
           leaf type {
             type identityref {
               base control-plane-protocol;
             }
             description
               "Type of the control-plane protocol.";
           }
           leaf name {
             type string;
             description
               "The name of the control-plane protocol instance.

                For system-controlled instances this name is persistent,
                i.e., it SHOULD NOT change across reboots.";
           }
         }
       }
       container ribs {
         description
           "Container for RIBs.";
         list rib {
           key "name";
           min-elements "1";
           description
             "Each entry represents a RIB identified by the 'name' key.
              All routes in a RIB MUST belong to the same address
              family.

              An implementation SHOULD provide one system-controlled
              default RIB for each supported address family.";
           leaf name {

             type string;
             description
               "The name of the RIB.";
           }
           uses address-family;
           leaf default-rib {
             if-feature "multiple-ribs";
             type boolean;
             default "true";
             description
               "This flag has the value of 'true' if and only if the RIB
                is the default RIB for the given address family.

                By default, control-plane protocols place their routes
                in the default RIBs.";
           }
           container routes {
             description
               "Current content of the RIB.";
             list route {
               description
                 "A RIB route entry.  This data node MUST be augmented
                  with information specific for routes of each address
                  family.";
               leaf route-preference {
                 type route-preference;
                 description
                   "This route attribute, also known as administrative
                    distance, allows for selecting the preferred route
                    among routes with the same destination prefix.  A
                    smaller value means a more preferred route.";
               }
               container next-hop {
                 description
                   "Route's next-hop attribute.";
                 uses next-hop-state-content;
               }
               uses route-metadata;
             }
           }
           action active-route {
             description
               "Return the active RIB route that is used for the
                destination address.

                Address-family-specific modules MUST augment input
                parameters with a leaf named 'destination-address'.";
             output {

               container route {
                 description
                   "The active RIB route for the specified destination.

                    If no route exists in the RIB for the destination
                    address, no output is returned.

                    Address-family-specific modules MUST augment this
                    container with appropriate route contents.";
                 container next-hop {
                   description
                     "Route's next-hop attribute.";
                   uses next-hop-state-content;
                 }
                 uses route-metadata;
               }
             }
           }
         }
       }
     }

     /* Configuration Data */

     container routing {
       description
         "Configuration parameters for the routing subsystem.";
       uses router-id {
         if-feature "router-id";
         description
           "Configuration of the global router ID.  Routing protocols
            that use router ID can use this parameter or override it
            with another value.";
       }
       container control-plane-protocols {
         description
           "Configuration of control-plane protocol instances.";
         list control-plane-protocol {
           key "type name";
           description
             "Each entry contains configuration of a control-plane
              protocol instance.";
           leaf type {
             type identityref {
               base control-plane-protocol;
             }
             description
               "Type of the control-plane protocol - an identity derived

                from the 'control-plane-protocol' base identity.";
           }
           leaf name {
             type string;
             description
               "An arbitrary name of the control-plane protocol
                instance.";
           }
           leaf description {
             type string;
             description
               "Textual description of the control-plane protocol
                instance.";
           }
           container static-routes {
             when "derived-from-or-self(../type, 'rt:static')" {
               description
                 "This container is only valid for the 'static' routing
                  protocol.";
             }
             description
               "Configuration of the 'static' pseudo-protocol.

                Address-family-specific modules augment this node with
                their lists of routes.";
           }
         }
       }
       container ribs {
         description
           "Configuration of RIBs.";
         list rib {
           key "name";
           description
             "Each entry contains configuration for a RIB identified by
              the 'name' key.

              Entries having the same key as a system-controlled entry
              of the list /routing-state/ribs/rib are used for
              configuring parameters of that entry.  Other entries
              define additional user-controlled RIBs.";
           leaf name {
             type string;
             description
               "The name of the RIB.

                For system-controlled entries, the value of this leaf
                must be the same as the name of the corresponding entry
                in state data.

                For user-controlled entries, an arbitrary name can be
                used.";
           }
           uses address-family {
             description
               "Address family of the RIB.

                It is mandatory for user-controlled RIBs.  For
                system-controlled RIBs it can be omitted; otherwise, it
                must match the address family of the corresponding state
                entry.";
             refine "address-family" {
               mandatory "false";
             }
           }
           leaf description {
             type string;
             description
               "Textual description of the RIB.";
           }
         }
       }
     }
   }

   <CODE ENDS>

8. IPv4 Unicast Routing Management YANG Module โœจ

okay bestie, this is the IPv4 one ๐ŸŽ€ It plugs IPv4 unicast into the ietf-routing module we already met, so you get IPv4 destination prefixes, next hops, the active-route action, and static routes all wrapped up with a bow ๐Ÿฆ‹

<CODE BEGINS> file "ietf-ipv4-unicast-routing@2016-11-04.yang"

module ietf-ipv4-unicast-routing {

  yang-version "1.1";

  namespace "urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing";

  prefix "v4ur";

  import ietf-routing {
    prefix "rt";
  }

  import ietf-inet-types {
    prefix "inet";
  }
  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>

     WG Chair: Lou Berger
               <mailto:lberger@labn.net>

     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>

     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>

     Editor:   Acee Lindem
               <mailto:acee@cisco.com>";

  description
    "This YANG module augments the 'ietf-routing' module with basic
     configuration and state data for IPv4 unicast routing.

     Copyright (c) 2016 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119.

     This version of this YANG module is part of RFC 8022;
     see the RFC itself for full legal notices.";

  revision 2016-11-04 {
    description
      "Initial revision.";
    reference
      "RFC 8022: A YANG Data Model for Routing Management";
  }
  /* Identities */

  identity ipv4-unicast {
    base rt:ipv4;
    description
      "This identity represents the IPv4 unicast address family.";
  }

  /* State data */

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route" {
    when "derived-from-or-self(../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";
    }
    description
      "This leaf augments an IPv4 unicast route.";
    leaf destination-prefix {
      type inet:ipv4-prefix;
      description
        "IPv4 destination prefix.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route/"
        + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
    when "derived-from-or-self(../../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";
    }
    description
      "Augment 'simple-next-hop' case in IPv4 unicast routes.";
    leaf next-hop-address {
      type inet:ipv4-address;
      description
        "IPv4 address of the next hop.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route/"
        + "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
        + "rt:next-hop-list/rt:next-hop" {
    when "derived-from-or-self(../../../../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";

    }
    description
      "This leaf augments the 'next-hop-list' case of IPv4 unicast
       routes.";
    leaf address {
      type inet:ipv4-address;
      description
        "IPv4 address of the next-hop.";
    }
  }

  augment
    "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/rt:input" {
    when "derived-from-or-self(../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast RIBs.";
    }
    description
      "This augment adds the input parameter of the 'active-route'
       action.";
    leaf destination-address {
      type inet:ipv4-address;
      description
        "IPv4 destination address.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route" {
    when "derived-from-or-self(../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";
    }
    description
      "This augment adds the destination prefix to the reply of the
       'active-route' action.";
    leaf destination-prefix {
      type inet:ipv4-prefix;
      description
        "IPv4 destination prefix.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route/rt:next-hop/rt:next-hop-options/"
        + "rt:simple-next-hop" {

    when "derived-from-or-self(../../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";
    }
    description
      "Augment 'simple-next-hop' case in the reply to the
       'active-route' action.";
    leaf next-hop-address {
      type inet:ipv4-address;
      description
        "IPv4 address of the next hop.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route/rt:next-hop/rt:next-hop-options/"
        + "rt:next-hop-list/rt:next-hop-list/rt:next-hop" {
    when "derived-from-or-self(../../../../../rt:address-family, "
       + "'v4ur:ipv4-unicast')" {
      description
        "This augment is valid only for IPv4 unicast.";
    }
    description
      "Augment 'next-hop-list' case in the reply to the
       'active-route' action.";
    leaf next-hop-address {
      type inet:ipv4-address;
      description
        "IPv4 address of the next hop.";
    }
  }

  /* Configuration data */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/rt:static-routes" {
    description
      "This augment defines the configuration of the 'static'
       pseudo-protocol with data specific to IPv4 unicast.";
    container ipv4 {
      description
        "Configuration of a 'static' pseudo-protocol instance
         consists of a list of routes.";
      list route {
        key "destination-prefix";
        description
          "A list of static routes.";

        leaf destination-prefix {
          type inet:ipv4-prefix;
          mandatory "true";
          description
            "IPv4 destination prefix.";
        }
        leaf description {
          type string;
          description
            "Textual description of the route.";
        }
        container next-hop {
          description
            "Configuration of next-hop.";
          uses rt:next-hop-content {
            augment "next-hop-options/simple-next-hop" {
              description
                "Augment 'simple-next-hop' case in IPv4 static
                 routes.";
              leaf next-hop-address {
                type inet:ipv4-address;
                description
                  "IPv4 address of the next hop.";
              }
            }
            augment "next-hop-options/next-hop-list/next-hop-list/"
                  + "next-hop" {
              description
                "Augment 'next-hop-list' case in IPv4 static
                 routes.";
              leaf next-hop-address {
                type inet:ipv4-address;
                description
                  "IPv4 address of the next hop.";
              }
            }
          }
        }
      }
    }
  }
}

<CODE ENDS>

9. IPv6 Unicast Routing Management YANG Module โœจ

okay bestie, this is the IPv6 sister of the IPv4 module we just did, so it's giving dรฉjร  vu but make it IPv6 ๐Ÿ’… it augments ietf-routing with the basic config and state stuff for IPv6 unicast routing ๐Ÿฆ‹

<CODE BEGINS> file "ietf-ipv6-unicast-routing@2016-11-04.yang"

module ietf-ipv6-unicast-routing {

  yang-version "1.1";

  namespace "urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing";

  prefix "v6ur";

  import ietf-routing {
    prefix "rt";
  }

  import ietf-inet-types {
    prefix "inet";
  }

  include ietf-ipv6-router-advertisements {
    revision-date 2016-11-04;
  }

  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>

     WG Chair: Lou Berger
               <mailto:lberger@labn.net>

     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>

     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>

     Editor:   Acee Lindem
               <mailto:acee@cisco.com>";

  description
    "This YANG module augments the 'ietf-routing' module with basic
     configuration and state data for IPv6 unicast routing.

     Copyright (c) 2016 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119.

     This version of this YANG module is part of RFC 8022;
     see the RFC itself for full legal notices.";

  revision 2016-11-04 {
    description
      "Initial revision.";
    reference
      "RFC 8022: A YANG Data Model for Routing Management";
  }

  /* Identities */

  identity ipv6-unicast {
    base rt:ipv6;
    description
      "This identity represents the IPv6 unicast address family.";
  }

  /* State data */

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route" {
    when "derived-from-or-self(../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "This leaf augments an IPv6 unicast route.";
    leaf destination-prefix {
      type inet:ipv6-prefix;
      description
        "IPv6 destination prefix.";
    }

  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route/"
        + "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
    when "derived-from-or-self(../../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "Augment 'simple-next-hop' case in IPv6 unicast routes.";
    leaf next-hop-address {
      type inet:ipv6-address;
      description
        "IPv6 address of the next hop.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route/"
        + "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
        + "rt:next-hop-list/rt:next-hop" {
    when "derived-from-or-self(../../../../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "This leaf augments the 'next-hop-list' case of IPv6 unicast
       routes.";
    leaf address {
      type inet:ipv6-address;
      description
        "IPv6 address of the next hop.";
    }
  }

  augment
    "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/rt:input" {
    when "derived-from-or-self(../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast RIBs.";
    }
    description
      "This augment adds the input parameter of the 'active-route'
       action.";
    leaf destination-address {
      type inet:ipv6-address;
      description
        "IPv6 destination address.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route" {
    when "derived-from-or-self(../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "This augment adds the destination prefix to the reply of the
       'active-route' action.";
    leaf destination-prefix {
      type inet:ipv6-prefix;
      description
        "IPv6 destination prefix.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route/rt:next-hop/rt:next-hop-options/"
        + "rt:simple-next-hop" {
    when "derived-from-or-self(../../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "Augment 'simple-next-hop' case in the reply to the
       'active-route' action.";
    leaf next-hop-address {
      type inet:ipv6-address;
      description
        "IPv6 address of the next hop.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route/rt:next-hop/rt:next-hop-options/"
        + "rt:next-hop-list/rt:next-hop-list/rt:next-hop" {
    when "derived-from-or-self(../../../../../rt:address-family, "
       + "'v6ur:ipv6-unicast')" {
      description
        "This augment is valid only for IPv6 unicast.";
    }
    description
      "Augment 'next-hop-list' case in the reply to the
       'active-route' action.";
    leaf next-hop-address {
      type inet:ipv6-address;
      description
        "IPv6 address of the next hop.";
    }
  }

  /* Configuration data */

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol/rt:static-routes" {
    description
      "This augment defines the configuration of the 'static'
       pseudo-protocol with data specific to IPv6 unicast.";
    container ipv6 {
      description
        "Configuration of a 'static' pseudo-protocol instance
         consists of a list of routes.";
      list route {
        key "destination-prefix";
        description
          "A list of static routes.";
        leaf destination-prefix {
          type inet:ipv6-prefix;
          mandatory "true";
          description
            "IPv6 destination prefix.";
        }
        leaf description {
          type string;
          description
            "Textual description of the route.";
        }
        container next-hop {
          description
            "Configuration of next-hop.";
          uses rt:next-hop-content {
            augment "next-hop-options/simple-next-hop" {
              description
                "Augment 'simple-next-hop' case in IPv6 static
                 routes.";
              leaf next-hop-address {
                type inet:ipv6-address;
                description
                  "IPv6 address of the next hop.";

              }
            }
            augment "next-hop-options/next-hop-list/next-hop-list/"
                  + "next-hop" {
              description
                "Augment 'next-hop-list' case in IPv6 static
                 routes.";
              leaf next-hop-address {
                type inet:ipv6-address;
                description
                  "IPv6 address of the next hop.";
              }
            }
          }
        }
      }
    }
  }
}

<CODE ENDS>

9.1. IPv6 Router Advertisements Submodule

ooh this one's the submodule that belongs to the IPv6 module ๐ŸŒธ it augments ietf-ip with config and state for IPv6 router advertisements, and it's giving main character energy in a supporting role ๐Ÿงš

<CODE BEGINS> file "ietf-ipv6-router-advertisements@2016-11-04.yang"

submodule ietf-ipv6-router-advertisements {

  yang-version "1.1";

  belongs-to ietf-ipv6-unicast-routing {
    prefix "v6ur";
  }

  import ietf-inet-types {
    prefix "inet";
  }

  import ietf-interfaces {
    prefix "if";
  }

  import ietf-ip {
    prefix "ip";
  }

  organization
    "IETF NETMOD (NETCONF Data Modeling Language) Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/netmod/>
     WG List:  <mailto:netmod@ietf.org>

     WG Chair: Lou Berger
               <mailto:lberger@labn.net>

     WG Chair: Kent Watsen
               <mailto:kwatsen@juniper.net>

     Editor:   Ladislav Lhotka
               <mailto:lhotka@nic.cz>

     Editor:   Acee Lindem
               <mailto:acee@cisco.com>";

  description
    "This YANG module augments the 'ietf-ip' module with
     configuration and state data of IPv6 router advertisements.

     Copyright (c) 2016 IETF Trust and the persons identified as
     authors of the code.  All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, is permitted pursuant to, and subject to
     the license terms contained in, the Simplified BSD License set
     forth in Section 4.c of the IETF Trust's Legal Provisions
     Relating to IETF Documents
     (http://trustee.ietf.org/license-info).

     The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
     NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and
     'OPTIONAL' in the module text are to be interpreted as described
     in RFC 2119.

     This version of this YANG module is part of RFC 8022;
     see the RFC itself for full legal notices.";

  reference
    "RFC 4861: Neighbor Discovery for IP version 6 (IPv6).";

  revision 2016-11-04 {
    description
      "Initial revision.";
    reference
      "RFC 8022: A YANG Data Model for Routing Management";
  }
  /* State data */

okay bestie, this is the YANG bit of the submodule and it's where the state data and the config data finally meet ๐Ÿ’…โœจ

     augment "/if:interfaces-state/if:interface/ip:ipv6" {
       description
         "Augment interface state data with parameters of IPv6 router
          advertisements.";
       container ipv6-router-advertisements {
         description
           "Parameters of IPv6 Router Advertisements.";
         leaf send-advertisements {
           type boolean;
           description
             "A flag indicating whether or not the router sends periodic
              Router Advertisements and responds to Router
              Solicitations.";
         }
         leaf max-rtr-adv-interval {
           type uint16 {
             range "4..1800";
           }
           units "seconds";
           description
             "The maximum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.";
         }
         leaf min-rtr-adv-interval {
           type uint16 {
             range "3..1350";
           }
           units "seconds";
           description
             "The minimum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.";
         }
         leaf managed-flag {
           type boolean;
           description
             "The value that is placed in the 'Managed address
              configuration' flag field in the Router Advertisement.";
         }
         leaf other-config-flag {
           type boolean;
           description
             "The value that is placed in the 'Other configuration' flag
              field in the Router Advertisement.";
         }
         leaf link-mtu {
           type uint32;
           description
             "The value that is placed in MTU options sent by the
              router.  A value of zero indicates that no MTU options are
              sent.";
         }
         leaf reachable-time {
           type uint32 {
             range "0..3600000";
           }
           units "milliseconds";
           description
             "The value that is placed in the Reachable Time field in
              the Router Advertisement messages sent by the router.  A
              value of zero means unspecified (by this router).";
         }
         leaf retrans-timer {
           type uint32;
           units "milliseconds";
           description
             "The value that is placed in the Retrans Timer field in the
              Router Advertisement messages sent by the router.  A value
              of zero means unspecified (by this router).";
         }

         leaf cur-hop-limit {
           type uint8;
           description
             "The value that is placed in the Cur Hop Limit field in the
              Router Advertisement messages sent by the router.  A value
              of zero means unspecified (by this router).";
         }
         leaf default-lifetime {
           type uint16 {
             range "0..9000";
           }
           units "seconds";
           description
             "The value that is placed in the Router Lifetime field of
              Router Advertisements sent from the interface, in seconds.
              A value of zero indicates that the router is not to be
              used as a default router.";
         }
         container prefix-list {
           description
             "A list of prefixes that are placed in Prefix Information
              options in Router Advertisement messages sent from the
              interface.

              By default, these are all prefixes that the router
              advertises via routing protocols as being on-link for the
              interface from which the advertisement is sent.";
           list prefix {
             key "prefix-spec";
             description
               "Advertised prefix entry and its parameters.";
             leaf prefix-spec {
               type inet:ipv6-prefix;
               description
                 "IPv6 address prefix.";
             }
             leaf valid-lifetime {
               type uint32;
               units "seconds";
               description
                 "The value that is placed in the Valid Lifetime in the
                  Prefix Information option.  The designated value of
                  all 1's (0xffffffff) represents infinity.

                  An implementation SHOULD keep this value constant in
                  consecutive advertisements except when it is
                  explicitly changed in configuration.";
             }
             leaf on-link-flag {
               type boolean;
               description
                 "The value that is placed in the on-link flag ('L-bit')
                  field in the Prefix Information option.";
             }
             leaf preferred-lifetime {
               type uint32;
               units "seconds";
               description
                 "The value that is placed in the Preferred Lifetime in
                  the Prefix Information option, in seconds.  The
                  designated value of all 1's (0xffffffff) represents
                  infinity.

                  An implementation SHOULD keep this value constant in
                  consecutive advertisements except when it is
                  explicitly changed in configuration.";
             }
             leaf autonomous-flag {
               type boolean;
               description
                 "The value that is placed in the Autonomous Flag field
                  in the Prefix Information option.";

             }
           }
         }
       }
     }

     /* Configuration data */

     augment "/if:interfaces/if:interface/ip:ipv6" {
       description
         "Augment interface configuration with parameters of IPv6 router
          advertisements.";
       container ipv6-router-advertisements {
         description
           "Configuration of IPv6 Router Advertisements.";
         leaf send-advertisements {
           type boolean;
           default "false";
           description
             "A flag indicating whether or not the router sends periodic
              Router Advertisements and responds to Router
              Solicitations.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvSendAdvertisements.";
         }
         leaf max-rtr-adv-interval {
           type uint16 {
             range "4..1800";
           }
           units "seconds";
           default "600";
           description
             "The maximum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MaxRtrAdvInterval.";
         }
         leaf min-rtr-adv-interval {
           type uint16 {
             range "3..1350";
           }
           units "seconds";
           must ". <= 0.75 * ../max-rtr-adv-interval" {
             description
               "The value MUST NOT be greater than 75% of
                'max-rtr-adv-interval'.";

           }
           description
             "The minimum time allowed between sending unsolicited
              multicast Router Advertisements from the interface.

              The default value to be used operationally if this leaf is
              not configured is determined as follows:

              - if max-rtr-adv-interval >= 9 seconds, the default
                value is 0.33 * max-rtr-adv-interval;

              - otherwise, it is 0.75 * max-rtr-adv-interval.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              MinRtrAdvInterval.";
         }
         leaf managed-flag {
           type boolean;
           default "false";
           description
             "The value to be placed in the 'Managed address
              configuration' flag field in the Router Advertisement.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvManagedFlag.";
         }
         leaf other-config-flag {
           type boolean;
           default "false";
           description
             "The value to be placed in the 'Other configuration' flag
              field in the Router Advertisement.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvOtherConfigFlag.";
         }
         leaf link-mtu {
           type uint32;
           default "0";
           description
             "The value to be placed in MTU options sent by the router.
              A value of zero indicates that no MTU options are sent.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvLinkMTU.";
         }
         leaf reachable-time {
           type uint32 {

             range "0..3600000";
           }
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Reachable Time field in the
              Router Advertisement messages sent by the router.  A value
              of zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvReachableTime.";
         }
         leaf retrans-timer {
           type uint32;
           units "milliseconds";
           default "0";
           description
             "The value to be placed in the Retrans Timer field in the
              Router Advertisement messages sent by the router.  A value
              of zero means unspecified (by this router).";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvRetransTimer.";
         }
         leaf cur-hop-limit {
           type uint8;
           description
             "The value to be placed in the Cur Hop Limit field in the
              Router Advertisement messages sent by the router.  A value
              of zero means unspecified (by this router).

              If this parameter is not configured, the device SHOULD use
              the value specified in IANA Assigned Numbers that was in
              effect at the time of implementation.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvCurHopLimit.

              IANA: IP Parameters,
              http://www.iana.org/assignments/ip-parameters";
         }
         leaf default-lifetime {
           type uint16 {
             range "0..9000";
           }
           units "seconds";
           description
             "The value to be placed in the Router Lifetime field of

              Router Advertisements sent from the interface, in seconds.
              It MUST be either zero or between max-rtr-adv-interval and
              9000 seconds.  A value of zero indicates that the router
              is not to be used as a default router.  These limits may
              be overridden by specific documents that describe how IPv6
              operates over different link layers.

              If this parameter is not configured, the device SHOULD use
              a value of 3 * max-rtr-adv-interval.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvDefaultLifeTime.";
         }
         container prefix-list {
           description
             "Configuration of prefixes to be placed in Prefix
              Information options in Router Advertisement messages sent
              from the interface.

              Prefixes that are advertised by default but do not have
              their entries in the child 'prefix' list are advertised
              with the default values of all parameters.
              The link-local prefix SHOULD NOT be included in the list
              of advertised prefixes.";
           reference
             "RFC 4861: Neighbor Discovery for IP version 6 (IPv6) -
              AdvPrefixList.";
           list prefix {
             key "prefix-spec";
             description
               "Configuration of an advertised prefix entry.";
             leaf prefix-spec {
               type inet:ipv6-prefix;
               description
                 "IPv6 address prefix.";
             }
             choice control-adv-prefixes {
               default "advertise";
               description
                 "Either the prefix is explicitly removed from the
                  set of advertised prefixes, or the parameters with
                  which it is advertised are specified (default case).";
               leaf no-advertise {
                 type empty;
                 description
                   "The prefix will not be advertised.

                    This can be used for removing the prefix from the
                    default set of advertised prefixes.";
               }
               case advertise {
                 leaf valid-lifetime {
                   type uint32;
                   units "seconds";
                   default "2592000";
                   description
                     "The value to be placed in the Valid Lifetime in
                      the Prefix Information option.  The designated
                      value of all 1's (0xffffffff) represents
                      infinity.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvValidLifetime.";
                 }
                 leaf on-link-flag {
                   type boolean;
                   default "true";
                   description
                     "The value to be placed in the on-link flag
                      ('L-bit') field in the Prefix Information
                      option.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvOnLinkFlag.";
                 }
                 leaf preferred-lifetime {
                   type uint32;
                   units "seconds";
                   must ". <= ../valid-lifetime" {
                     description
                       "This value MUST NOT be greater than
                        valid-lifetime.";
                   }
                   default "604800";
                   description
                     "The value to be placed in the Preferred Lifetime
                      in the Prefix Information option.  The designated
                      value of all 1's (0xffffffff) represents
                      infinity.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvPreferredLifetime.";
                 }
                 leaf autonomous-flag {
                   type boolean;
                   default "true";
                   description
                     "The value to be placed in the Autonomous Flag
                      field in the Prefix Information option.";
                   reference
                     "RFC 4861: Neighbor Discovery for IP version 6
                      (IPv6) - AdvAutonomousFlag.";
                 }
               }
             }
           }
         }
       }
     }
   }

   <CODE ENDS>

10. IANA Considerations ๐ŸŽ€

Okay, time for the registry paperwork ๐Ÿ“ This document registers the following namespace URIs in the "IETF XML Registry" [RFC3688]:

   URI: urn:ietf:params:xml:ns:yang:ietf-routing
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.

   URI: urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.

   URI: urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.

This document also registers the following YANG modules in the "YANG Module Names" registry [RFC6020]:

   Name:         ietf-routing
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-routing
   Prefix:       rt
   Reference:    RFC 8022

   Name:         ietf-ipv4-unicast-routing
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing
   Prefix:       v4ur
   Reference:    RFC 8022
   Name:         ietf-ipv6-unicast-routing
   Namespace:    urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing
   Prefix:       v6ur
   Reference:    RFC 8022

And last but not least, one YANG submodule goes into that same "YANG Module Names" registry [RFC6020] โœจ

   Name:         ietf-ipv6-router-advertisements
   Module:       ietf-ipv6-unicast-routing
   Reference:    RFC 8022

11. Security Considerations ๐Ÿ”

Okay, this part is serious, bestie ๐Ÿ˜ญ Configuration and state data that follow the core routing data model (defined in this document) are designed to be reached through a management protocol with a secure transport layer, such as NETCONF [RFC6241]. The NETCONF access control model [RFC6536] gives you the tools to restrict particular NETCONF users to a preset subset of all the available NETCONF protocol operations and content.

A bunch of configuration data nodes defined in the YANG modules in the core routing data model are writable, creatable, and deletable (aka config true in YANG terms, which is the default) ๐Ÿ™ˆ Those nodes can be sensitive or vulnerable in some network environments. Write operations on them, like edit-config in NETCONF, can cause real trouble for the network if the protocol operations aren't properly protected.

The vulnerable config true parameters and subtrees are:

  • /routing/control-plane-protocols/control-plane-protocol: This list specifies the control-plane protocols configured on a device.
  • /routing/ribs/rib: This list specifies the RIBs configured for the device.
Unauthorized access to either of these lists can seriously hurt the routing subsystem of both the local device and the network ๐Ÿ’€ That could mean network malfunctions, packets getting delivered to the wrong destinations, and other chaos.

12. References ๐Ÿ“š

12.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <http://www.rfc-editor.org/info/rfc3688>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <http://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <http://www.rfc-editor.org/info/rfc6991>.

   [RFC7223]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
              <http://www.rfc-editor.org/info/rfc7223>.

   [RFC7277]  Bjorklund, M., "A YANG Data Model for IP Management",
              RFC 7277, DOI 10.17487/RFC7277, June 2014,
              <http://www.rfc-editor.org/info/rfc7277>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <http://www.rfc-editor.org/info/rfc7950>.

12.2. Informative References

   [RFC6087]  Bierman, A., "Guidelines for Authors and Reviewers of YANG
              Data Model Documents", RFC 6087, DOI 10.17487/RFC6087,
              January 2011, <http://www.rfc-editor.org/info/rfc6087>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <http://www.rfc-editor.org/info/rfc6536>.

   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
              <http://www.rfc-editor.org/info/rfc7895>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <http://www.rfc-editor.org/info/rfc7951>.

Appendix A. The Complete Data Trees ๐ŸŒˆ

This appendix shows the full configuration and state data trees of the core routing data model. Check out Section 2.2 for a breakdown of the symbols used ๐Ÿฆ‹ The data type of every leaf node sits near the right end of its line, so you can see exactly what you're working with โœจ

A.1. Configuration Data ๐Ÿ’œ

   +--rw routing
      +--rw router-id?                 yang:dotted-quad
      +--rw control-plane-protocols
      |  +--rw control-plane-protocol* [type name]
      |     +--rw type             identityref
      |     +--rw name             string
      |     +--rw description?     string
      |     +--rw static-routes
      |        +--rw v6ur:ipv6
      |        |  +--rw v6ur:route* [destination-prefix]
      |        |     +--rw v6ur:destination-prefix    inet:ipv6-prefix
      |        |     +--rw v6ur:description?          string
      |        |     +--rw v6ur:next-hop
      |        |        +--rw (v6ur:next-hop-options)
      |        |           +--:(v6ur:simple-next-hop)
      |        |           |  +--rw v6ur:outgoing-interface?
      |        |           |  +--rw v6ur:next-hop-address?
      |        |           +--:(v6ur:special-next-hop)
      |        |           |  +--rw v6ur:special-next-hop?   enumeration
      |        |           +--:(v6ur:next-hop-list)
      |        |              +--rw v6ur:next-hop-list
      |        |                 +--rw v6ur:next-hop* [index]
      |        |                    +--rw v6ur:index              string
      |        |                    +--rw v6ur:outgoing-interface?
      |        |                    +--rw v6ur:next-hop-address?
      |        +--rw v4ur:ipv4
      |           +--rw v4ur:route* [destination-prefix]
      |              +--rw v4ur:destination-prefix    inet:ipv4-prefix
      |              +--rw v4ur:description?          string
      |              +--rw v4ur:next-hop
      |                 +--rw (v4ur:next-hop-options)
      |                    +--:(v4ur:simple-next-hop)
      |                    |  +--rw v4ur:outgoing-interface?
      |                    |  +--rw v4ur:next-hop-address?
      |                    +--:(v4ur:special-next-hop)
      |                    |  +--rw v4ur:special-next-hop?   enumeration
      |                    +--:(v4ur:next-hop-list)
      |                       +--rw v4ur:next-hop-list
      |                          +--rw v4ur:next-hop* [index]
      |                             +--rw v4ur:index              string
      |                             +--rw v4ur:outgoing-interface?
      |                             +--rw v4ur:next-hop-address?
      +--rw ribs
         +--rw rib* [name]
            +--rw name              string
            +--rw address-family?   identityref
            +--rw description?      string

A.2. State Data ๐Ÿ‘€

okay so this is the state side of the tree, the bit that shows what the router is actually doing right now ๐Ÿ”ฅ Everything is read-only (+--ro) except the RPC active-route (+---x), which has a writable input. The augments from the IPv4 and IPv6 modules show up as v4ur: and v6ur: prefixes, so you can see which module each leaf came from. It's giving organised ๐Ÿ’…

+--ro routing-state
|  +--ro router-id?                 yang:dotted-quad
|  +--ro interfaces
|  |  +--ro interface*   if:interface-state-ref
|  +--ro control-plane-protocols
|  |  +--ro control-plane-protocol* [type name]
|  |     +--ro type    identityref
|  |     +--ro name    string
|  +--ro ribs
|     +--ro rib* [name]
|        +--ro name              string
|        +--ro address-family    identityref
|        +--ro default-rib?      boolean {multiple-ribs}?
|        +--ro routes
|        |  +--ro route*
|        |     +--ro route-preference?          route-preference
|        |     +--ro next-hop
|        |     |  +--ro (next-hop-options)
|        |     |     +--:(simple-next-hop)
|        |     |     |  +--ro outgoing-interface?
|        |     |     |  +--ro v6ur:next-hop-address?
|        |     |     |  +--ro v4ur:next-hop-address?
|        |     |     +--:(special-next-hop)
|        |     |     |  +--ro special-next-hop?        enumeration
|        |     |     +--:(next-hop-list)
|        |     |        +--ro next-hop-list
|        |     |           +--ro next-hop*
|        |     |              +--ro outgoing-interface?
|        |     |              +--ro v6ur:address?
|        |     |              +--ro v4ur:address?
|        |     +--ro source-protocol            identityref
|        |     +--ro active?                    empty
|        |     +--ro last-updated?              yang:date-and-time
|        |     +--ro v6ur:destination-prefix?   inet:ipv6-prefix
|        |     +--ro v4ur:destination-prefix?   inet:ipv4-prefix
|        +---x active-route
|           +---w input
|           |  +---w v6ur:destination-address?   inet:ipv6-address
|           |  +---w v4ur:destination-address?   inet:ipv4-address
|           +--ro output
|              +--ro route
|                 +--ro next-hop
|                 |  +--ro (next-hop-options)
|                 |     +--:(simple-next-hop)
|                 |     |  +--ro outgoing-interface?
|                 |     |  +--ro v6ur:next-hop-address?
|                 |     |  +--ro v4ur:next-hop-address?
|                 |     +--:(special-next-hop)
|                 |     |  +--ro special-next-hop?     enumeration
|                 |     +--:(next-hop-list)
|                 |        +--ro next-hop-list
|                 |           +--ro next-hop*
|                 |              +--ro outgoing-interface?
|                 |              +--ro v6ur:next-hop-address?
|                 |              +--ro v4ur:next-hop-address?
|                 +--ro source-protocol            identityref
|                 +--ro active?                    empty
|                 +--ro last-updated?           yang:date-and-time
|                 +--ro v6ur:destination-prefix?  inet:ipv6-prefix
|                 +--ro v4ur:destination-prefix?  inet:ipv4-prefix

Appendix B. Minimum Implementation ๐ŸŒธ

bestie, not every router is a giant backbone box ๐Ÿซถ Some parts of the core routing model, like user-defined RIBs, are really meant for advanced routers. This appendix is a casual, non-normative set of tips for building the bare minimum of features, which is perfect for hosts or super simple routers ๐Ÿ“

So the minimum version skips the multiple-ribs feature. That means you get exactly one system-controlled RIB per address family (IPv4, IPv6, or both), and those RIBs are also the default ones. No user-controlled RIBs allowed, sorry, not sorry ๐Ÿ™ˆ

Besides the mandatory direct pseudo-protocol, a minimum implementation should support configuring instances of the static pseudo-protocol. Cute and simple โœจ

For hosts that are never meant to act as routers, you should take out the ability to turn on sending IPv6 router advertisements (Section 5.4). Nobody needs a host yelling "I'm a router!" ๐Ÿ’€

And if the platform is seriously low on resources, it can use deviations to restrict the data model, like limiting how many static control-plane protocol instances there are. Totally valid, very practical ๐Ÿ’œ


Appendix C. Example: Adding a New Control-Plane Protocol ๐Ÿงš

okay this one is my favourite ๐Ÿ˜ญ It shows how you can extend the core routing data model to support a brand-new control-plane protocol. The YANG module example-rip below is only an illustration, not a real data model for the Routing Information Protocol (RIP) ๐ŸŽ€ It also doesn't follow every guideline in [RFC6087], because it's trying to stay short. See also Section 5.3.2 if you want the full rules ๐Ÿฆ‹

module example-rip {

  yang-version "1.1";

  namespace "http://example.com/rip";

  prefix "rip";

  import ietf-interfaces {
    prefix "if";
  }

  import ietf-routing {
    prefix "rt";
  }

  identity rip {
    base rt:routing-protocol;
    description
      "Identity for the Routing Information Protocol (RIP).";
  }

  typedef rip-metric {
    type uint8 {
      range "0..16";
    }
  }

  grouping route-content {
    description
      "This grouping defines RIP-specific route attributes.";
    leaf metric {
      type rip-metric;
    }
    leaf tag {

      type uint16;
      default "0";
      description
        "This leaf may be used to carry additional info, e.g.,
         autonomous system (AS) number.";
    }
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:routes/rt:route" {
    when "derived-from-or-self(rt:source-protocol, 'rip:rip')" {
      description
        "This augment is only valid for a route whose source
         protocol is RIP.";
    }
    description
      "RIP-specific route attributes.";
    uses route-content;
  }

  augment "/rt:routing-state/rt:ribs/rt:rib/rt:active-route/"
        + "rt:output/rt:route" {
    description
      "RIP-specific route attributes in the output of 'active-route'
       RPC.";
    uses route-content;
  }

  augment "/rt:routing/rt:control-plane-protocols/"
        + "rt:control-plane-protocol" {
    when "derived-from-or-self(rt:type,'rip:rip')" {
      description
        "This augment is only valid for a routing protocol instance
         of type 'rip'.";
    }
    container rip {
      presence "RIP configuration";
      description
        "RIP instance configuration.";
      container interfaces {
        description
          "Per-interface RIP configuration.";
        list interface {
          key "name";
          description
            "RIP is enabled on interfaces that have an entry in this
             list, unless 'enabled' is set to 'false' for that
             entry.";
          leaf name {

            type if:interface-ref;
          }
          leaf enabled {
            type boolean;
            default "true";
          }
          leaf metric {
            type rip-metric;
            default "1";
          }
        }
      }
      leaf update-interval {
        type uint8 {
          range "10..60";
        }
        units "seconds";
        default "30";
        description
          "Time interval between periodic updates.";
      }
    }
  }
}

Appendix D. Data Tree Example โœจ

okay so this appendix is the example bestie ๐Ÿ’– It shows an instance data tree in the JSON encoding [RFC7951], and it has both configuration and state data in it ๐ŸŽ€ The data follows a data model that's defined by the YANG library spec [RFC7895], so here's the yang library bit first:

{
  "ietf-yang-library:modules-state": {
    "module-set-id": "c2e1f54169aa7f36e1a6e8d0865d441d3600f9c4",
    "module": [
      {
        "name": "ietf-routing",
        "revision": "2016-11-04",
        "feature": [
          "multiple-ribs",
          "router-id"
        ],
        "namespace": "urn:ietf:params:xml:ns:yang:ietf-routing",
        "conformance-type": "implement"
      },
      {
        "name": "ietf-ipv4-unicast-routing",
        "revision": "2016-11-04",
        "namespace":
          "urn:ietf:params:xml:ns:yang:ietf-ipv4-unicast-routing",
        "conformance-type": "implement"
      },
      {
        "name": "ietf-ipv6-unicast-routing",
        "revision": "2016-11-04",
        "namespace":
          "urn:ietf:params:xml:ns:yang:ietf-ipv6-unicast-routing",
        "conformance-type": "implement"
      },
      {
        "name": "ietf-interfaces",
        "revision": "2014-05-08",
        "namespace": "urn:ietf:params:xml:ns:yang:ietf-interfaces",
        "conformance-type": "implement"
      },
      {
        "name": "ietf-inet-types",
        "namespace": "urn:ietf:params:xml:ns:yang:ietf-inet-types",
        "revision": "2013-07-15",
        "conformance-type": "import"
      },
      {
        "name": "ietf-yang-types",
        "namespace": "urn:ietf:params:xml:ns:yang:ietf-yang-types",
        "revision": "2013-07-15",
        "conformance-type": "import"
      },
      {
        "name": "iana-if-type",
        "namespace": "urn:ietf:params:xml:ns:yang:iana-if-type",
        "revision": "",
        "conformance-type": "implement"
      },
      {
        "name": "ietf-ip",
        "revision": "2014-06-16",
        "namespace": "urn:ietf:params:xml:ns:yang:ietf-ip",
        "conformance-type": "implement"
      }
    ]
  }
}

picture this setup, as shown in Figure 3 ๐Ÿงš router "A" uses static default routes with the "ISP" router as its next hop. IPv6 router advertisements are configured only on the "eth1" interface, and they're disabled on the upstream "eth0" interface. so cute, right? ๐Ÿฆ‹

                +-----------------+
                |                 |
                |    Router ISP   |
                |                 |
                +--------+--------+
                         |2001:db8:0:1::2
                         |192.0.2.2
                         |
                         |
                         |2001:db8:0:1::1
                     eth0|192.0.2.1
                +--------+--------+
                |                 |
                |     Router A    |
                |                 |
                +--------+--------+
                     eth1|198.51.100.1
                         |2001:db8:0:2::1
                         |

Figure 3: Example of Network Configuration

so the instance data tree could look something like this ๐Ÿ’…

{
  "ietf-interfaces:interfaces": {
    "interface": [
      {
        "name": "eth0",
        "type": "iana-if-type:ethernetCsmacd",
        "description": "Uplink to ISP.",
        "ietf-ip:ipv4": {
          "address": [
            {
              "ip": "192.0.2.1",
              "prefix-length": 24
            }
          ],
          "forwarding": true
        },
        "ietf-ip:ipv6": {
          "address": [
            {

              "ip": "2001:0db8:0:1::1",
              "prefix-length": 64
            }
          ],
          "forwarding": true,
          "autoconf": {
            "create-global-addresses": false
          }
        }
      },
      {
        "name": "eth1",
        "type": "iana-if-type:ethernetCsmacd",
        "description": "Interface to the internal network.",
        "ietf-ip:ipv4": {
          "address": [
            {
              "ip": "198.51.100.1",
              "prefix-length": 24
            }
          ],
          "forwarding": true
        },
        "ietf-ip:ipv6": {
          "address": [
            {
              "ip": "2001:0db8:0:2::1",
              "prefix-length": 64
            }
          ],
          "forwarding": true,
          "autoconf": {
            "create-global-addresses": false
          },
          "ietf-ipv6-unicast-routing:ipv6-router-advertisements": {
            "send-advertisements": true
          }
        }
      }
    ]
  },
  "ietf-interfaces:interfaces-state": {
    "interface": [
      {
        "name": "eth0",
        "type": "iana-if-type:ethernetCsmacd",
        "phys-address": "00:0C:42:E5:B1:E9",
        "oper-status": "up",
        "statistics": {
          "discontinuity-time": "2015-10-24T17:11:27+02:00"
        },
        "ietf-ip:ipv4": {
          "forwarding": true,
          "mtu": 1500,
          "address": [
            {
              "ip": "192.0.2.1",
              "prefix-length": 24
            }
          ]
        },
        "ietf-ip:ipv6": {
          "forwarding": true,
          "mtu": 1500,
          "address": [
            {
              "ip": "2001:0db8:0:1::1",
              "prefix-length": 64
            }
          ],
          "ietf-ipv6-unicast-routing:ipv6-router-advertisements": {
            "send-advertisements": false
          }
        }
      },
      {
        "name": "eth1",
        "type": "iana-if-type:ethernetCsmacd",
        "phys-address": "00:0C:42:E5:B1:EA",
        "oper-status": "up",
        "statistics": {
          "discontinuity-time": "2015-10-24T17:11:29+02:00"
        },
        "ietf-ip:ipv4": {
          "forwarding": true,
          "mtu": 1500,
          "address": [
            {
              "ip": "198.51.100.1",
              "prefix-length": 24
            }
          ]
        },
        "ietf-ip:ipv6": {
          "forwarding": true,
          "mtu": 1500,
          "address": [
            {
              "ip": "2001:0db8:0:2::1",
              "prefix-length": 64
            }
          ],
          "ietf-ipv6-unicast-routing:ipv6-router-advertisements": {
            "send-advertisements": true,
            "prefix-list": {
              "prefix": [
                {
                  "prefix-spec": "2001:db8:0:2::/64"
                }
              ]
            }
          }
        }
      }
    ]
  },
  "ietf-routing:routing": {
    "router-id": "192.0.2.1",
    "control-plane-protocols": {
      "control-plane-protocol": [
        {
          "type": "ietf-routing:static",
          "name": "st0",
          "description":
            "Static routing is used for the internal network.",
          "static-routes": {
            "ietf-ipv4-unicast-routing:ipv4": {
              "route": [
                {
                  "destination-prefix": "0.0.0.0/0",
                  "next-hop": {
                    "next-hop-address": "192.0.2.2"
                  }
                }
              ]
            },
            "ietf-ipv6-unicast-routing:ipv6": {
              "route": [
                {
                  "destination-prefix": "::/0",
                  "next-hop": {
                    "next-hop-address": "2001:db8:0:1::2"
                  }
                }

              ]
            }
          }
        }
      ]
    }
  },
  "ietf-routing:routing-state": {
    "interfaces": {
      "interface": [
        "eth0",
        "eth1"
      ]
    },
    "control-plane-protocols": {
      "control-plane-protocol": [
        {
          "type": "ietf-routing:static",
          "name": "st0"
        }
      ]
    },
    "ribs": {
      "rib": [
        {
          "name": "ipv4-master",
          "address-family":
            "ietf-ipv4-unicast-routing:ipv4-unicast",
          "default-rib": true,
          "routes": {
            "route": [
              {
                "ietf-ipv4-unicast-routing:destination-prefix":
                  "192.0.2.1/24",
                "next-hop": {
                  "outgoing-interface": "eth0"
                },
                "route-preference": 0,
                "source-protocol": "ietf-routing:direct",
                "last-updated": "2015-10-24T17:11:27+02:00"
              },
              {
                "ietf-ipv4-unicast-routing:destination-prefix":
                  "198.51.100.0/24",
                "next-hop": {
                  "outgoing-interface": "eth1"
                },
                "source-protocol": "ietf-routing:direct",
                "route-preference": 0,
                "last-updated": "2015-10-24T17:11:27+02:00"
              },
              {
                "ietf-ipv4-unicast-routing:destination-prefix":
                  "0.0.0.0/0",
                "source-protocol": "ietf-routing:static",
                "route-preference": 5,
                "next-hop": {
                  "ietf-ipv4-unicast-routing:next-hop-address":
                    "192.0.2.2"
                },
                "last-updated": "2015-10-24T18:02:45+02:00"
              }
            ]
          }
        },
        {
          "name": "ipv6-master",
          "address-family":
            "ietf-ipv6-unicast-routing:ipv6-unicast",
          "default-rib": true,
          "routes": {
            "route": [
              {
                "ietf-ipv6-unicast-routing:destination-prefix":
                  "2001:db8:0:1::/64",
                "next-hop": {
                  "outgoing-interface": "eth0"
                },
                "source-protocol": "ietf-routing:direct",
                "route-preference": 0,
                "last-updated": "2015-10-24T17:11:27+02:00"
              },
              {
                "ietf-ipv6-unicast-routing:destination-prefix":
                  "2001:db8:0:2::/64",
                "next-hop": {
                  "outgoing-interface": "eth1"
                },
                "source-protocol": "ietf-routing:direct",
                "route-preference": 0,
                "last-updated": "2015-10-24T17:11:27+02:00"
              },
              {
                "ietf-ipv6-unicast-routing:destination-prefix":
                  "::/0",
                "next-hop": {

                  "ietf-ipv6-unicast-routing:next-hop-address":
                    "2001:db8:0:1::2"
                },
                "source-protocol": "ietf-routing:static",
                "route-preference": 5,
                "last-updated": "2015-10-24T18:02:45+02:00"
              }
            ]
          }
        }
      ]
    }
  }
}

Acknowledgments ๐Ÿซถ

Okay bestie, the authors wanted to give a huge shoutout to everyone who helped make this better ๐Ÿ’– Nitin Bahadur, Martin Bjorklund, Dean Bogdanovic, Jeff Haas, Joel Halpern, Wes Hardaker, Sriganesh Kini, David Lamparter, Andrew McGregor, Jan Medved, Xiang Li, Stephane Litkowski, Thomas Morin, Tom Petch, Yingzhen Qu, Bruno Rijsman, Juergen Schoenwaelder, Phil Shafer, Dave Thaler, Yi Yang, Derek Man-Kit Yeung, and Jeffrey Zhang all left helpful comments and suggestions, and the document is so much better because of them ๐Ÿ‘‘ Literal main character energy from this whole crew โœจ


Authors' Addresses ๐Ÿ’Œ

Meet the two people who wrote this one ๐ŸŽ€

Ladislav Lhotka ๐ŸŒธ CZ.NIC Email: lhotka@nic.cz

Acee Lindem ๐Ÿฆ‹ Cisco Systems Email: acee@cisco.com

Bookmark these if you ever want to reach out with questions, bestie ๐Ÿ“ฌ๐Ÿ’œ

๐Ÿ“ฆ where this page comes from