[SOLVED] Router advertisements on CARP not advertising IPv6 prefix

[shadowlaw]

Hi,

I have a CARP setup with a single public IPv4 and a /48 prefix, received over PPPoE. Everything on the v4 side is working well, including failover. On the IPv6 side, I have created a VIP interface using fe80:: as address, and I am advertising that address as the source for router advertisements - as recommend in the CARP IPv6 setup documentation.

My problem however is that only the master will include my IPv6 prefix in the router advertisements; the backup presumably does not announce it, because I only have a single IPv4 address, and so the backup itself does not have an active IPv6 connection (or a prefix), until it takes over as master. This means that IPv6 clients tend to get confused when the last RA is from the backup, since it does not contain any prefix. When the next RA is sent by the master, clients will work correctly again.

Since my prefix is (in theory) static, is there a way to manually configure radvd to just always announce this prefix, regardless of the state of the WAN interface? Or are there better ways of solving this?

[franco]

IMO this only works relatively well with static IPv6 prefix and manual IPv6 assignments on the LAN side.

You can't really force a disconnected backup to include a range that it doesn't have acquired (yet) -- especially if it's dynamic.


Cheers,
Franco

[shadowlaw]

IMO this only works relatively well with static IPv6 prefix and manual IPv6 assignments on the LAN side.

Thanks! I know how to set static IPv6 assignments on the LAN side, but how can I configure the static IPv6 prefix? Would I need to enable DHCPv6 on the LAN?

[Patrick M. Hausen]

Set a static IPv6 address on OPNsense and enable router advertisements.

[franco]

Given your prefix is static still use DHCPv6, but don't set LAN IPv6 to track and assign one /64 from the prefix.


Cheers,
Franco

[shadowlaw]

Thanks a lot, this seems to work!

[franco]

Ok keep in mind to do this on both master and backup and check if your prefix is really static (unless you are sure by contract that it is).


Cheers,
Franco

[shadowlaw]

Ok keep in mind to do this on both master and backup and check if your prefix is really static (unless you are sure by contract that it is).

Yeah it's one of those 'you get your prefix and it really should never change, but we cannot promise anything'. So far it has been stable, though.