Description of problem:
IPv6 support in OVN has few missing features. It would be good to add a section about IPv6 here - https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/13/html-single/networking_with_open_virtual_network/
OSP13 with OVN supports creating IPv6 networks. However there are a couple of issues
1. Prefix delegation is not yet supported in OVN. So the user has to create private IPv6 subnets with the appropriate GUA prefixes manually.
2. There is no default route added by networking-ovn to route the traffic to gateway IP of the IPv6 public network subnet. Without this, the North-South routing will not work if the VM wants to send a N/S packet with the IPv6 destination IP which doesn't belong to the IPv6 public subnet. - https://bugs.launchpad.net/networking-ovn/+bug/1808753
Version-Release number of selected component (if applicable):
Steps to Reproduce: