Allowas-in in BIRD - possible to implement?

[Alex Bligh]

--On 1 July 2011 13:47:50 +0200 Adrian Czapek <adrian.czapek at rybnet.pl> 
wrote:

> Default route might not be such effective when you have more then one
> upstream provider, since you have to choose default route throu one of
> them, and if you have bad luck and both internal connection and this
> particular provider will fail at the same time, you're toasted.

So, the standard solution here is originate the default route(s)
conditionally. In OSPF you can tie them to the interfaces going
up and down (which doesn't help much if the session dies). In BGP
that's harder if I remember correctly, but there was a Cisco knob
I used a while ago; I'm afraid I forget which.

A more serious problem is that if your AS is partitioned, you need
to have routes to subnets of your summary/aggregate block unless
your aggregate block's numbering divides well with the partition.
Even accepting own AS is not in general a fix here because the
routes tend to be too long to avoid filtering by the upstream. As
there is not a lot of traffic here (but what there is is important),
sometimes tunnels work.

-- 
Alex Bligh