NM-OPENVSWITCH(7)

📦
version 1.58.0 · 12 versions
, in centos-stream 10

✨ nm-openvswitch(7) ✨ — the whole vibe check on NetworkManager's Open vSwitch era 💅

okay bestie, so this is nm-openvswitch, section 7 of the manual, and it's literally the overview of NetworkManager's Open vSwitch support. grab a drink 🍓, we're going in.

🌈 OVERVIEW 🌈

So here's the tea: NetworkManager has basic Open vSwitch support — and it's genuinely good enough to set up simple Open vSwitch configurations. 🎀 But no cap, it is not extensive, and it does not expose all the functionality that Open vSwitch provides. For large or complicated deployments, users are advised (read: strongly encouraged, bestie 🫶) to use the native tools shipped with Open vSwitch. This document is here to give you the overview of what NetworkManager currently provides, its capabilities and its limitations. iykyk.

First and foremost — and this is the main character fact of the whole page: NetworkManager applies the configuration by modifying the OVSDB directly. Its configuration model follows the OVSDB database model closely, and it does not give you the level of abstraction that ovs-vsctl provides. different vibes entirely. 💀

In practical terms, that means the following:

  • NetworkManager only ever talks to a single OVSDB instance via an UNIX domain socket.
  • The configuration is made up of Bridges, Ports and Interfaces. Interfaces are always attached to Ports, and Ports are always attached to Bridges. that's the whole hierarchy, periodt.
  • NetworkManager only creates Bridges, Ports and Interfaces you ask it to. Unlike ovs-vsctl, it doesn't create the local interface nor its port automatically. no surprise guests here 🙈
  • You can't attach an Interface directly to a Bridge. You always need a Port, even if it has just one interface.
  • There are no VLANs. The VLAN tagging is enabled by setting a ovs-port.tag property on a Port.
  • There are no bonds either. The bonding is enabled by enslaving multiple Interfaces to a Port and configured by setting properties on a port.

🌉 Bridges 🌉

Bridges are represented by connections of ovs-bridge type. Due to the limitations of OVSDB, "empty" Bridges (with no Ports) can't exist. NetworkManager inserts the records for Bridges into OVSDB when a Port is attached.

⚠️ Known limitation: when the last NetworkManager's owned port is removed, the bridge is removed too — even if there are other externally attached ports. 😭 she takes the whole bridge with her.

🚪 Ports 🚪

Ports are represented by connections of ovs-port type. Due to the limitations of OVSDB, "empty" Ports (with no Interfaces) can't exist. Ports can also be configured to do VLAN tagging or Bonding. NetworkManager inserts the records for Ports into OVSDB when an Interface is attached. And yeah — Ports must be attached to a Bridge. non-negotiable 💅

⚠️ Known limitation: when the last NetworkManager's owned interface is removed, the port is removed too — even if there are other externally attached interfaces. same energy, different layer. 💀

🧚 Interfaces 🧚

Interfaces are represented by a connections attached to a Port. The system interfaces (the ones that have a corresponding Linux link) have a respective connection.type of the link (e.g. "wired", "bond", "dummy", etc.). Other interfaces ("internal" or "patch" interfaces) are of ovs-interface type. The OVSDB entries are inserted upon attachment to a Port. ✨

🎀 EXAMPLES 🎀

Example 1. Creating a Bridge with a single internal Interface

$ nmcli conn add type ovs-bridge conn.interface bridge0
Connection 'ovs-bridge-bridge0' (d10fc64d-1d48-4394-a1b8-e1aea72f27d5) successfully added.
$ nmcli conn add type ovs-port conn.interface port0 controller bridge0
Connection 'ovs-port-port0' (5ae22bae-bba4-4815-9ade-7e635633e1f0) successfully added.
$ nmcli conn add type ovs-interface port-type ovs-port conn.interface iface0 \
  controller port0 ipv4.method manual ipv4.address 192.0.2.1/24
Connection 'ovs-interface-iface0' (3640d2a1-a2fd-4718-92f1-cffadb5b6cdc) successfully added.

As said above, you need to create a Port even for a single interface. also — before you add the Interface, the Bridge and Port devices appear active, but are not configured in OVSDB yet. sneaky, right? 👀 You can inspect the results with ovs-vsctl show.

Example 2. Adding a Linux interface to a Bridge

$ nmcli conn add type ovs-port conn.interface port1 controller bridge0
Connection 'ovs-port-port1' (67d041eb-8e7b-4458-afee-a1d07c9c4552) successfully added.
$ nmcli conn add type ethernet conn.interface eth0 controller port1
Connection 'ovs-slave-eth0' (d459c45c-cf78-4c1c-b4b7-505e71379624) successfully added.

Again, you need a port. yes, still. every single time. 🫠

Example 3. Creating a VLAN

$ nmcli conn add type ovs-port conn.interface port2 controller bridge0 ovs-port.tag 120
Connection 'ovs-port-port2' (3994c093-4ef7-4549-a4fd-627b831c3cb8) successfully added.
$ nmcli conn add type ethernet conn.interface eth1 controller port2
Connection 'ovs-slave-eth1' (099be06e-71ad-484d-8d5a-fcadc5f207f5) successfully added.

It's just a port with a tag. iconic, honestly. 💅

Example 4. Creating a Bond

$ nmcli conn add type ovs-port conn.interface bond0 controller bridge0
Connection 'ovs-port-bond0' (d154ebf9-e999-4e1b-a084-a3de53d25d8a) successfully added.
$ nmcli conn add type ethernet conn.interface eth2 controller bond0
Connection 'ovs-slave-eth2' (475ac1bf-30b2-4534-a877-27f33f58b082) successfully added.
$ nmcli conn add type ethernet conn.interface eth3 controller bond0
Connection 'ovs-slave-eth3' (8dedeecb-ed12-482b-b77a-24a4fb835136) successfully added.

It's just a Port with multiple interfaces. 🧚 see the nm-settings-nmcli manual for the Bonding options you can use with "nmcli c add" or "nmcli c modify". And you could even set a VLAN tag on the same Port to do VLAN tagging and bonding at the same time. multitasking queen 👑

💀 BUGS 💀

  • Not all Open vSwitch capabilities are supported. 😭
  • Open vSwitch devices don't expose many useful properties on D-Bus.
  • Probably many more.

🔗 SEE ALSO 🔗

RFC 7047: The Open vSwitch Database Management Protocol[1], ovs-vsctl(8), ovs-vswitchd.conf.db(5), nm-settings-nmcli(5), nmcli(1)

📝 NOTES 📝

  1. RFC 7047: The Open vSwitch Database Management Protocol https://www.rfc-editor.org/rfc/rfc7047.txt

and that's the whole page, bestie 🫶 this one's brought to you by NetworkManager 1.58.0 — go forth and bridge responsibly ✨🌉💜

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