ICMP weirdness

Bill Stewart nonobvious at gmail.com
Tue Oct 19 02:32:43 UTC 2004

AT&T normally rejects bogons such as RFC1918, urpf-detected forgeries
from customers,
traffic pointed at internal network routers, etc.  However, AT&T's
network does support MPLS,
so if InsightBB is part of the Comcast cloud, it may be that this
_looks_ like the public internet
but is really an MPLS private network cloud that happens to use
similar addresses and
only reaches the Internet through gateways, in spite of being carried
on much of the same hardware.

Disclaimer:  As a Comcast stockholder, I probably should know their architecture
and whether or not InsightBB is part of their company,
but all I really know about it is that cable companies have a history
of doing funky things,
particularly with NAT, which is one of many reasons I use DSL at home
instead of cable modems.  And this posting is strictly my private
speculation, not my employer's.

          Bill Stewart

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