General question on rfc1918

Sean Donelan sean at
Tue Nov 13 16:12:41 UTC 2007

On Tue, 13 Nov 2007, Drew Weaver wrote:
> Is it to be expected to see rfc1918 src'd packets coming from transit carriers?

Yes.  Any ISP which uses RFC1918 on "internal" links may generate 
various ICMP error packets (e.g. traceroute/TTL expire, PMTU 
discovery/Fragmentation required, etc) from router interfaces which have
RFC1918 addresses for transit traffic.

Some people filter them anyway, and get "*"'s in traceroutes and PMTU 

#include "old debate about using RFC1918 addresses on transit links"
#include "other old debate about filtering stuff in backbones or edge"

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