Is there way to disable IPv6 default route received via SLAAC/DHCP6/RA?

General questions
1

Here is the situation:

  • Our backup provider is Starlink
  • They provide /64 and /56 IPv6 subnets
  • The /56 is intended for PD and we don’t use/request it
  • And for /64 network we request address via SLAAC/DHCP6
  • However, we also receive a default route with the address (likely via RA)

And this is the problem - for DHCPv4 I can specify - no-default-route or default-route-distance options and they actually work as intended… but I could not find how to achieve the same for IPv6… Technically default route information should come from RA protocol and not DHCPv6 or SLAAC but short of running the interface in a separate VRF (which comes with its own set of problems), I could not find a way to get rid of the default route.

The worst part is that the default route is installed as kernel route with highest priority and there is no way to work around it with metrics and administrative distances :frowning:

Am I missing something?

2

Ha, you’re in the other camp! There was a bug/feature with 1.4.3 where learning a v6 default stopped working with the same config, let me find the Phabricator for it. I can’t recall the final outcome, but certainly it’d been discussed in depth.

Ahhh here it is.

3

It is actually more similar to this Issues with default route on Starlink and this ⚓ T4405 DHCP client sometimes ignores `no-default-route` option of an interface …but for IPv6.

4

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