[Babel-users] IPv6 ULA GUA S2S routing problem

[Jochen Demmer]

Hi,

I've been wondering if a dynamic routing solution like babel might help
me in this situation.

Havnig two sites, Home (A) and Data Center (B). I rely heavily on IPv6,
do as little v4 as possible. So up until today I'm running two static
/48 GUA prefixes at both sites.
In order to migrate to a faster fiber connection on A I will soon loose
my static prefix. I'm running a wireguard tunnel between both sites
which currently routes statically.

Now my idea was to migrate to ULA at A. The problem with that approach
though is that hosts in A will use their GUA address they as a source
address, which will result in asymmetric routing. A host will contact B
host and return packets will try to run outside the tunnel as there is
no route. Rules will prevent that data from arriving, which is of
course wanted behaviour. I want to run all the traffic between the
sites through tunnel.

I though I could use babeld to just fill that gap and always have a
route to the prefix I get at home. So even when there is a disconnect
and a new prefix, I thought babeld will just fetch it and push it over
to site B.

Is that a valid idea? If so, what would a configuration will look like?
Do I just have to configure the wireguard interface on both sites or
will I have to add filters?

Thank you!
Jochen