I had to replace a host on our SolusVM cluster, and I created a new host and went to restore some VPS servers.  Everything looked good, I was able to login and see all the VPS servers running but found my IPv6 wasn’t working on just these VPS servers, when I know it has been working before.

This is what were running:
SolusVM 1.20.01
CentOS Linux release 7.4.1708

My IPv4 was working fine but after I stored a VPS to a new host my IPv6 isn’t working correctly.

I tracked the issue down to there was configuration lines missing from my interace.  Noramlly these would be in ifcfg-em1, however our SolusVM servers use xenbr0 as a bridged interface.  I added the following 4 lines to the interface config. 

vi /etc/sysconfig/network-scripts/ifcfg-xenbr0

In that file I added the following lines:

IPV6INIT=yes
IPV6_AUTOCONF=yes
NETWORKING_IPV6=yes
IPV6FORWARDING=yes

Then restarted the network interface

systemctl restart network

After that my VPS started responding to IPv6 ping requests.