RFC 1388
RIP Version 2 Carrying Additional Information
RIP Version 2 Carrying Additional Information 🎀
Network Working Group 💖 Request for Comments: 1388 ✨
- Author: G. Malkin, Xylogics, Inc. 💅
- Category: IAB standards track protocol 🔥
- Date: January 1993 🌸
- Updates: RFC 1058 🦋 (its header doesn't list anything it obsoletes)
Status of this Memo ✨
okay so this one is an IAB standards track protocol for the Internet community, and it's literally asking for discussion and suggestions for improvements 🫶 For the standardization state and status of this protocol, go check the current edition of the "IAB Official Protocol Standards" (that's the source of truth, bestie 📚). Distribution of this memo is unlimited 🌈
Abstract 🦋
this doc extends the Routing Information Protocol (RIP), as defined in [1], so RIP packets can carry way more useful info and get a measure of security 🔐 A companion document will define the SNMP MIB objects for RIP-2 [2] 💜
Acknowledgements 🫶
huge thanks to Fred Baker, Noel Chiappa and Vince Fuller for their contributions 😭 This memo is a product of the RIP-2 Working Group of the Internet Engineering Task Force (IETF) ✨
Table of Contents 📖
1. Justification . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Current RIP . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . . 2
3.1 Authentication . . . . . . . . . . . . . . . . . . . . . . . 3
3.2 Routing Domain . . . . . . . . . . . . . . . . . . . . . . . 4
3.3 Route Tag . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4 Subnet Mask . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.5 Next Hop . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.6 Multicasting . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1 Compatibility Switch . . . . . . . . . . . . . . . . . . . . 5
4.2 Authentication . . . . . . . . . . . . . . . . . . . . . . . 6
4.3 Larger Infinity . . . . . . . . . . . . . . . . . . . . . . . 6
4.4 Addressless Links . . . . . . . . . . . . . . . . . . . . . . 6
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Security Considerations . . . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 71. Justification 🍓
okay so with OSPF and IS-IS showing up, some people are like "RIP is obsolete" 💀 And honestly? The newer IGP routing protocols are way superior to RIP. BUT RIP still has some main-character advantages 👑 Mainly, in a small network, RIP has very little overhead in terms of bandwidth used and configuration and management time. It's also super easy to implement, especially compared to the newer IGPs 🧚
Also, there are many, many more RIP implementations out in the field than OSPF and IS-IS combined 😭 That's likely to stay true for some years yet.
So since RIP is gonna be useful in lots of environments for a while, it makes total sense to make RIP more useful 💅 This is especially true since the gain is way bigger than the cost of the change ✨
2. Current RIP 🌸
the current RIP packet carries the minimal amount of info routers need to route packets through a network. It also has a big chunk of unused space, which is giving history and origins 🙈
The current RIP protocol doesn't consider autonomous systems, IGP/EGP interactions, subnetting, or authentication, because implementations of those came after RIP did 🫠 The lack of subnet masks is a seriously big problem for routers, since they need a subnet mask to know how to determine a route. If a RIP route is a network route (all non-network bits 0), the subnet mask equals the network mask. But if some of the non-network bits are set, the router can't determine the subnet mask. Worse still, the router can't tell whether the RIP route is a subnet route or a host route. Right now, some routers just pick the subnet mask of the interface the route was learned over, and figure out the route type from that 😬
3. Protocol Extensions 🦋
this doc does not change the RIP protocol per se. Instead, it adds extensions to the datagram format so routers can share important additional info 💜
the new RIP datagram format looks like this:
0 1 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Command (1) | Version (1) | Routing Domain (2) |
+---------------+---------------+-------------------------------+
| Address Family Identifier (2) | Route Tag (2) |
+-------------------------------+-------------------------------+
| IP Address (4) |
+---------------------------------------------------------------+
| Subnet Mask (4) |
+---------------------------------------------------------------+
| Next Hop (4) |
+---------------------------------------------------------------+
| Metric (4) |
+---------------------------------------------------------------+The Command, Address Family Identifier (AFI), IP Address, and Metric all keep the meanings defined in RFC 1058 🫶 The Version field will specify version number 2 for RIP datagrams that use authentication or carry info in any of the newly defined fields ✨
All fields are coded in IP network byte order (big-endian) 🔢
3.1. Authentication 🔐
okay the vibe here: authentication is a per packet function, and there's only one 2-byte field available in the packet header. Any reasonable authentication scheme needs more than two bytes, so the authentication scheme for RIP version 2 uses the space of an entire RIP entry 💅 If the Address Family Identifier of the first (and only the first) entry in the packet is 0xFFFF, then the remainder of that entry contains the authentication. That means there can be, at most, 24 RIP entries in the remainder of the packet 🧮 If authentication isn't in use, then no entries in the packet should have an Address Family Identifier of 0xFFFF. A RIP packet that contains an authentication entry would look like this:
0 1 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Command (1) | Version (1) | Routing Domain (2) |
+---------------+---------------+-------------------------------+
| 0xFFFF | Authentication Type (2) |
+-------------------------------+-------------------------------+
~ Authentication (16) ~
+---------------------------------------------------------------+Currently, the only Authentication Type is simple password, and it's type 2 🔑 The remaining 16 bytes hold the plain text password. If the password is under 16 bytes, it must be left-justified and padded to the right with nulls (0x00) 🩵
3.2. Routing Domain 🌈
The Routing Domain (RD) number is the number of the routing process that this update belongs to 🧚 This field is used to associate the routing update with a specific routing process on the receiving router. The RD is needed so multiple, independent RIP "clouds" can co-exist on the same physical wire 🫧 This gives administrators the ability to run multiple, possibly parallel, instances of RIP to implement simple policy 📋 That means a router operating within one routing domain, or a set of routing domains, should ignore RIP packets that belong to another routing domain 🚫 RD 0 is the default routing domain 💖
3.3. Route Tag 🏷️
The Route Tag (RT) field exists as support for EGPs 🌸 The contents and use of this field are outside the scope of this protocol. However, it's expected that the field will be used to carry Autonomous System numbers for EGP and BGP ✨ Any RIP system that receives a RIP entry containing a non-zero RT value must re-advertise that value. Routes that have no RT value must advertise an RT value of zero 💅
3.4. Subnet mask 🎀
The Subnet Mask field contains the subnet mask applied to the IP address to yield the non-host portion of the address. If this field is zero, then no subnet mask has been included for this entry 🫶
On an interface where a RIP-1 router may hear and operate on the info in a RIP-2 routing entry, the following two rules apply 🚨
- Information internal to one network must never be advertised into another network, and
- information about a more specific subnet may not be advertised where RIP-1 routers would consider it a host route.
3.5. Next Hop 🦋
The immediate next hop IP address that packets to the destination specified by this route entry should be forwarded to 🏃♀️ Specifying a value of 0.0.0.0 in this field indicates that routing should be via the originator of the RIP advertisement. An address specified as a next hop must, per force, be directly reachable on the logical subnet over which the advertisement is made 💜
The whole purpose of the Next Hop field is to stop packets from being routed through extra hops in the system ✨ It's especially useful when RIP isn't being run on all of the routers on a network. A simple example is given in Appendix A 📖 Note that Next Hop is an "advisory" field. That means if the provided info is ignored, a possibly sub-optimal, but absolutely valid, route may be taken 🤷♀️
3.6. Multicasting 📡
To cut down on unnecessary load on those hosts that aren't listening to RIP-2 packets, an IP multicast address will be used for periodic broadcasts 🫧 The IP multicast address is 224.0.0.9. Note that IGMP is not needed, since these are inter-router messages that aren't forwarded 🙅♀️
To keep backwards compatibility, the use of the multicast address will be configurable, as described in section 4.1 ⚙️ If multicasting is used, it should be used on all interfaces that support it 🌈
4. Compatibility 🫶
RFC 1058 showed considerable forethought in how it specifies handling of version numbers 🧠 It specifies that RIP packets of version 0 are to be discarded, that RIP packets of version 1 are to be discarded if any Must Be Zero (MBZ) field is non-zero, and that RIP packets of any version greater than 1 should not be discarded simply because an MBZ field contains a value other than zero. This means the new version of RIP is totally backwards compatible with existing RIP implementations that adhere to this part of the specification 🥹✨
4.1. Compatibility Switch 🔀
A compatibility switch is necessary for two reasons 🩷 First, there are implementations of RIP-1 in the field that don't follow RFC 1058 as described above. Second, the use of multicasting would stop RIP-1 systems from receiving RIP-2 updates, which may be a desired feature in some cases 🙈
The switch has three settings 🎛️ RIP-1, where only RIP-1 packets are sent. RIP-1 compatibility, where RIP-2 packets are broadcast. And RIP-2, where RIP-2 packets are multicast. The recommended default for this switch is RIP-1 compatibility 💜
4.2. Authentication ✨
okay so bestie 🫶 an authentication entry is tagged with an Address Family Identifier of 0xFFFF, and a RIP-1 system is like "not me… that's not IP" and just ignores it 💅 since it belongs to an address family other than IP. ngl that's kinda iconic. BUT (and this part matters 👀) using authentication will not stop RIP-1 systems from seeing RIP-2 packets. heads up. if you want that, it can be done with multicasting, as described in sections 3.6 and 4.1 🦋
4.3. Larger Infinity 🌈
ok while we're on the compatibility vibes 🎀, people have literally asked for one thing: a bigger infinity ✨. the main reason we can't do it is that it would break backwards compatibility 💀. a larger infinity would totally confuse older versions of rip. at best they'd ignore the route, the same way they'd ignore a metric of 16 🙈
there was also a proposal to make the Metric a single byte and reuse the high three bytes, but that would break any implementations that treat the metric as a long 😭 not a vibe.
4.4. Addressless Links 🍓
just like RIP-1, addressless links are a no-go for RIP-2 🙅 no exceptions, bestie.
Appendix A 🧚
this is a simple example of how the next hop field gets used in a rip entry 🌸
----- ----- ----- ----- ----- -----
|IR1| |IR2| |IR3| |XR1| |XR2| |XR3|
--+-- --+-- --+-- --+-- --+-- --+--
| | | | | |
--+-------+-------+---------------+-------+-------+--
<-------------RIP-2------------->okay picture this 👀 IR1, IR2, and IR3 are all "internal" routers under one administration (like a campus) that picked RIP-2 as its IGP 🎓. XR1, XR2, and XR3, on the other hand, belong to a separate administration (like a regional network that the campus is a member of) and use some other routing protocol (like OSPF) 🌐. XR1, XR2, and XR3 trade routing info with each other, so they know the best routes to networks N1 and N2 go via XR1, to N3, N4, and N5 go via XR2, and to N6 and N7 go via XR3.
by setting the Next Hop field correctly (to XR2 for N3/N4/N5, to XR3 for N6/N7), only XR1 needs to swap RIP-2 routes with IR1/IR2/IR3 for routing to happen without extra hops through XR1 ✨ that's the slay. without the Next Hop (say, if RIP-1 were used), XR2 and XR3 would also have to join the RIP-2 protocol to get rid of those extra hops 💀
References 📚
[1] Hedrick, C., "Routing Information Protocol", RFC 1058, Rutgers University, June 1988.
[2] Malkin, G., and F. Baker, "RIP Version 2 MIB Extension", RFC 1389, Xylogics, Inc., Advanced Computer Communications, January 1993.
[3] Malkin, G., "RIP Version 2 Protocol Analysis", RFC 1387, Xylogics, Inc., January 1993.
Security Considerations 🚨
this section is serious, bestie 😱 the basic RIP protocol is not a secure protocol. to bring RIP-2 in line with more modern routing protocols, an extensible authentication mechanism has been incorporated into the protocol enhancements 🔐 this mechanism is described in sections 3.1 and 4.2.
Author's Address 💌
Gary Scott Malkin
Xylogics, Inc.
53 Third Avenue
Burlington, MA 01803
Phone: (617) 272-8140
EMail: gmalkin@Xylogics.COMand that's a wrap on RIP-2 🌈💖✨
📦 where this page comes from
- ietf: rfc1388 1993-01
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms