Dual Homed BGP

Sat Jan 25 14:15:05 UTC 2020

lør. 25. jan. 2020 13.42 skrev Tore Anderson <tore at fud.no>:

> * Baldur Norddahl
>
> > If you join any peering exchanges, full tables will be mandatory. Some
> parties will export prefixes and then expect a more specific prefix
> received from your transit to override a part of the space received via the
> peering.
>
> That would be a fundamentally flawed expectation, in my opinion.
>

I do not disagree, however the real world sometimes works differently. Like
anycast, people break the rules and gets away with it.

In any case, this is from a recent personal experience. We had a problem
that led us to drop full tables and run with a default for a while. Nobody
noticed the difference, which is why I can confidently say that unless you
need the full tables for something, the advantages are somewhat overstated.

However one customer found a reachability problem. Turns out that a peer
was exporting a /19 prefix through a peering session with us and at another
site they exported a /24 from the same space with no routing between sites.

Regards

Baldur

>
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