Bird2 not distributing IPv6 address on dummy to OSPF

[Ondrej Zajicek]

On Tue, Sep 28, 2021 at 11:04:28AM +0200, Blažej Krajňák wrote:
> Hello everyone,
> 
> I just found that neighbour router Mikrotik has the LSA in table. So I
> incorrectly mentioned that Bird2 is not advertising route. But that
> route does not appear in Mikrotik routing table. I compared the same
> configuration with Quagga (which works correctly) and the difference
> between LSAs is LA option bit.

Hello

I also bumped into this issue. You are right, BIRD sets LA-bit for /128
prefixes, Mikrotik for some reason ignores them. AFAIK when modified to
not set LA-bit, it worked.

Simple workaround is to export the prefix as an external route:

protocol static {
    ipv6
    route 20xx:xxxx:xxxx::1/128 via "dummy0" { ospf_metric1 = 0; };
}

> According to RFC5340:
> 
> LA-bit
>       The "local address" capability bit.  If set, the prefix is
>       actually an IPv6 interface address of the Advertising Router.
>       Advertisement of local interface addresses is described in
>       Section 4.4.3.9.  An implementation MAY also set the LA-bit for
>       prefixes advertised with a host PrefixLength (128).
> 
> So does it mean that Mikrotik does not understand "MAY implementation"
> of LA-bit for host PrefixLength (128)?

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."