Create custom OVN underlay network

The underlay network is the physical network infrastructure that provides connectivity between the nodes in an OVN deployment and is responsible for carrying encapsulated traffic between OVN components through Geneve (Generic Network Virtualization Encapsulation) tunnels. This allows the virtual network traffic to be transported over the physical underlay network. Now, by default, MicroOVN uses the hostname of a cluster member as a Geneve endpoint to set up the underlay network, but it is also possible to use custom Geneve endpoints for the cluster members.

Set up the underlay network

To tell MicroOVN to use the underlay network, you need to provide the IP address of the underlay network interface on each node. Let us assume that we want to create a three-node OVN cluster and that each node has a dedicated interface eth1 with an IP address. Let says that 10.0.1.{2,3,4} are the respective addresses on the eth1 interface on each node. You can set the underlay network IP address in the init :

microovn init

Example of the interaction:

root@micro1:~# microovn init
Please choose the address MicroOVN will be listening on [default=10.242.68.93]:
Would you like to create a new MicroOVN cluster? (yes/no) [default=no]: yes
Please choose a name for this system [default=micro1]:
Would you like to define a custom encapsulation IP address for this member? (yes/no) [default=no]: yes
Please enter the custom encapsulation IP address for this member: 10.0.1.2
Would you like to add additional servers to the cluster? (yes/no) [default=no]: yes
What's the name of the new MicroOVN server? (empty to exit): micro2
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What's the name of the new MicroOVN server? (empty to exit): micro3
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What's the name of the new MicroOVN server? (empty to exit):

root@micro2:~# microovn init
Please choose the address MicroOVN will be listening on [default=10.242.68.13]:
Would you like to create a new MicroOVN cluster? (yes/no) [default=no]: no
Please enter your join token: eyJzZWNyZXQiOiJmOWU1OWU0N2Q1M2E0ZjJlYTYzNWYwMzIzYTE5ZTgyMjEyMzA3ZmJmY2U5OTRiOTk3NzQ4ZTAyM2VmOGEyN2MyIiwiZmluZ2VycHJpbnQiOiJlZGY0MzEzY2ZkOWFiMTdmYWIwZTZkMmE3MWZiNGZlM2U5M2RjZTBjNzNhYTQ4NWI3ZTk2Zjk2YzBhZmZlOWU2Iiwiam9pbl9hZGRyZXNzZXMiOlsiMTAuMjQyLjY4LjkzOjY0NDMiXX0=
Would you like to define a custom encapsulation IP address for this member? (yes/no) [default=no]: yes
Please enter the custom encapsulation IP address for this member: 10.0.1.3

root@micro3:~# microovn init
Please choose the address MicroOVN will be listening on [default=10.242.68.170]:
Would you like to create a new MicroOVN cluster? (yes/no) [default=no]:
Please enter your join token: eyJzZWNyZXQiOiI5MWYzODUyZTA4ZjQyOWQxNGE2Y2JiZWI0NGNmODkyMjRjNzUzZjU1NjYzYTY3MjE5ZjZkMmVhOGM0MTdhM2YxIiwiZmluZ2VycHJpbnQiOiJlZGY0MzEzY2ZkOWFiMTdmYWIwZTZkMmE3MWZiNGZlM2U5M2RjZTBjNzNhYTQ4NWI3ZTk2Zjk2YzBhZmZlOWU2Iiwiam9pbl9hZGRyZXNzZXMiOlsiMTAuMjQyLjY4LjkzOjY0NDMiXX0=
Would you like to define a custom encapsulation IP address for this member? (yes/no) [default=no]: yes
Please enter the custom encapsulation IP address for this member: 10.0.1.4

Now, the MicroOVN cluster is configured to use the underlay network with the IP addresses 10.0.1.{2,3,4} on each node as tunnel endpoint for the encapsulated traffic. To verify that the underlay network is correctly configured, you can check the IP of OVN Geneve tunnel endpoint on each node:

root@micro1:~# microovn.ovs-vsctl get Open_vSwitch . external_ids:ovn-encap-ip
"10.0.1.2"

root@micro2:~# microovn.ovs-vsctl get Open_vSwitch . external_ids:ovn-encap-ip
"10.0.1.3"

root@micro3:~# microovn.ovs-vsctl get Open_vSwitch . external_ids:ovn-encap-ip
"10.0.1.4"