BGP and aggregation

In the referenced message, Ralph Doncaster said:

> BGP will discard any prefix with its own AS in the path, for loop
> prevention. Hence, one half of the AS would still be unable to
> reach the other half. This is why a partitioned AS is a failure
> condition. A tunnel is a means to keep the AS nonpartitioned.

I was thinking of doing iBGP over my transit connections (with a couple
of static routes so the iBGP works) AND over my inter-city circuit. Any
reason why this won't work?

-Ralph

The loss of igp metric will make it untenable at best. Do it over a
GRE tunnel, with your regular igp (isis, ospf, eigrp, or shudder rip).

default routes have their own problems which only treat the symptoms
of a partitioned as, rather than the problem.

> I was thinking of doing iBGP over my transit connections (with a couple
> of static routes so the iBGP works) AND over my inter-city circuit. Any
> reason why this won't work?
>
> -Ralph

The loss of igp metric will make it untenable at best. Do it over a
GRE tunnel, with your regular igp (isis, ospf, eigrp, or shudder rip).

As far as I can tell, GRE doesn't support fragmentation -
i.e. encapsulation of a 1500-byte IP packet that results in a GRE packet
larger than the interface MTU size.

-Ralph

set your mtu on your gre's to 1514