Re: Bogon list

[Joe Abley <jabley () automagic org>]

On Tuesday, June 4, 2002, at 12:48 , Barry Raveendran Greene wrote:

> > Then we come to the extra bogons like exchange point allocations. Can't
> > forget them. :)
>
> I've never heard anyone refer to the IXP allocations as "bogons." Plus, 
> I've
> not heard of anyone filtering the IXP prefixes on their ingress peering
> filters. Egress peering filters - yes.

Depending on your internal routing policy, it may well be important not 
to learn routes to exchange points to which you connect.

A straightforward example is when people accidentally propagate the 
prefixes 195.66.224.0/24 and 195.66.225.0/24. Interfaces on the LINX 
exchange fabric are currently numbered within 195.66.224.0/23, so if my 
LINX router learns the longer prefix routes from somewhere else, my EBGP 
sessions across the exchange get hijacked. Without the prefix length 
aspect the effect is less obviously serious, but it can still cause 
issues.

Subnets numbering interfaces on exchange point subnets, for exchange 
points at which I participate, can hence generally be considered 
bogonish by me. For exchange points at which I do not participate this 
need not be the case. The list of EP-derived bogons is, following this 
logic, operator-specific.


Joe