At 09:35 PM 1/25/02 -0600, you wrote: Mmmmmm... this trace is from an @Work/Excite circuit that is about to go dark. The "cable modem" is (as far as I can tell) the Cisco 2600 at the customer site. Either that or @Work's customer gateway address.

Cable modems actually "have" two IP's: one rfc1918 that they use for provisioning purposes and in the actual IP of the cable modem device, one real IP that they pass on to the end-user's device. Many of the newer cable modems are now showing the private IP in traces where previously they'd pass and not respond to ICMP. As for why, who knows? My best guess is to ease tracking down offending IP's vs. users.

Michael Graham

-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Turpin, Mark Sent: Friday, January 25, 2002 8:43 PM To: 'Simon Higgs'; 'nanog@merit.edu' Subject: RE: Routing through non-addressable space???

Routing through a cable interface that has a 10.x address as its primary ip address would be my first guess, esp. due to the 24.x address.

! int cable3/0 ip address 10.x.x.x. x.x.x.x.x ip address public.for.cpe.equip mask.mask.mask.mask secondary

cheers,

Mark Turpin Charter NOC mturpin@chartercom.com

-----Original Message----- From: Simon Higgs [mailto:simon@higgs.com] Sent: Friday, January 25, 2002 8:47 PM To: nanog@merit.edu Subject: Routing through non-addressable space???

Can someone explain this trace to me. How on earth did the 10.0.0.0 network get inserted into the last hop?

# IP address Host name Round trip time

4 24.130.2.243 GSR1-SRP4-0.lsanhe4.we.mediaone.net 64 ms 5 24.130.2.242 GSR2-SRP4-0.lsanhe3.we.mediaone.net 71 ms 6 12.125.98.13 Unavailable 79 ms 7 12.123.28.94 gbr2-p100.la2ca.ip.att.net 94 ms 8 No response 9 12.122.11.226 ggr1-p340.la2ca.ip.att.net 110 ms 10 192.205.32.246 att-gw.la.home.net 112 ms 11 24.7.74.182 wbb1-pos2-0.pop1.ca.home.net 120 ms 12 10.252.25.118 Unavailable 134 ms 13 209.125.128.80 Unavailable 141 ms

Best Regards, Simon -- ###