Description of problem:

When Virtual Machine using dynmiac ipv6 configuration is using primary UDN layer2 it ends up with multipath ipv6 default gw, since all the gateway routers from this topology are answering back the Router Solicitation.

This has two main problems:

• All the VM north/south traffic will flow inter node
• If one of the node is down it will affect north/south traffic, this is very common after live migration done to repair or replace a node.

Version-Release number of selected component (if applicable): 4.18

How reproducible: Always

Steps to Reproduce:

1. Start a kubevirt virtual machine with dynamic ipv6 configuation dhcp+slaac
2. Dump ipv6 routes with "ip -6 route"

Actual results:

  Default gw has multi path pointing to each of the gateway routers ipv6 link local address

Expected results:

  Default gw need to point to the gateway router where the VM is running, that's include the different gateway router after migration.

Additional info:

There are some WIP's at ovn-k fixing it while the proper OVN transit router topology lands:

• https://issues.redhat.com/browse/SDN-5424
• https://issues.redhat.com/browse/SDN-5435
• https://issues.redhat.com/browse/SDN-5515

Proper solution is to use the future OVN topology "transit router" that's being developed here https://issues.redhat.com/browse/FDP-872.