[c-nsp] rfc1918 from ISP

[Justin M. Streiner]

On Wed, 17 May 2006, adrian kok wrote:

> Our router is running BGP and connecting to our
> upstream provider with /30 network.   Our log reveals
> that there are private IP addresses reaching our
> router's interface that is facing our upstream ISP.
> How could this be possible?  Should upstream ISP be
> blocking private IP address according to standard
> configuration?  Could the packet be stripped and IP be
> converted somehow during the transition? It happens in
> many Tier-1 ISP though !

It sounds like your upstream provider is not filtering out RFC1918 address 
space - they should be.  You can also filter packets with RFC1918 and 
unassigned address space from entering and leaving your network.

If you mean that your upstream provider is announcing (leaking) routes for 
non-routable address ranges to you via BGP, 1) let them know - they should 
not be doing this and something is broken, 2) filter them out on your 
side.  You should also have filters in place to prevent you from doing the 
same to them.

jms