RIR filtering & Level3

Thu Nov 15 14:03:25 UTC 2007

Justin Shore wrote:

> So, that said, what is everyone else doing to perform sanity checks on 
> their learned routes?  Are a good many implementing RIR filtering and 
> dropping everything smaller than a /24?  L3 of course isn't the only 
> source of these tiny routes but it's so obvious I saw it and wasn't even 
> looking for it.  This would explain why I'm getting so many more routes 
> from L3 too.  I'm getting 232k from AT&T, 233.5k from Cox and 244k from L3.

Two sides to this coin:

1) ProviderX (L3 in this case) is allowing you to see some of their 
internal routing information.  If by chance those more-specifics come 
with MED and you have multiple connections to them, you can choose to 
make intelligent routing decisions via MED.  You could have circuitous 
routing though, should you not get the more-specifics over a subset of 
your connections

2) ProviderX is demonstrating their incompetence in routing and 
filtering.  This is just an inkling of the goofy stuff and potential 
landmines lurking within their network.  You should open tickets, 
escalate to management, and abandon this provider ASAP.

Reality?  Probably middle ground here.  You could choose to filter them 
by prefix length and let it be, or _ask_ them what's up.

My $0.02,

Pete