ICMP weirdness

Mon Oct 18 21:02:53 UTC 2004

Jim Popovitch wrote:

>>From Comcast Cable, at my home in Atlanta, I can ping 10.10.1.1....
> which is pong'ed from a private client network hanging somewhere off of
> Insight Broadband's network in the North Central part of the US.  Why on
> god's green earth do network operators allow such nonsense as this?

FWIW, I get the same result from Comcast residential coax
service from Santa Clara, CA using a plain ol' *nix UDP
traceroute. (This is not ICMP specific.)

raceroute 10.10.1.1
traceroute to 10.10.1.1 (10.10.1.1), 64 hops max, 44 byte packets
[snip my internal net]
  3  12.244.25.145 (12.244.25.145)  17.315 ms  17.378 ms  17.492 ms
  4  12.244.67.17 (12.244.67.17)  33.548 ms  23.702 ms  13.066 ms
  5  12.244.72.206 (12.244.72.206)  21.554 ms  18.118 ms  18.589 ms
  6  gbr2-p50.sffca.ip.att.net (12.123.13.62)  23.677 ms  31.973 ms  18.647 ms
  7  tbr1-p012702.sffca.ip.att.net (12.122.11.69)  24.447 ms  19.266 ms  19.036 ms
  8  tbr1-cl2.sl9mo.ip.att.net (12.122.10.41)  73.801 ms  66.745 ms  71.541 ms
  9  gbr2-p10.sl9mo.ip.att.net (12.122.11.102)  68.524 ms  62.157 ms  66.172 ms
10  gar1-p370.sl9mo.ip.att.net (12.123.24.213)  68.568 ms  65.325 ms  62.455 ms
11  12-220-0-69.client.insightBB.com (12.220.0.69)  93.072 ms  98.102 ms  91.132 ms
12  12-220-7-198.client.insightBB.com (12.220.7.198)  88.131 ms  83.943 ms  85.713 ms
13  10.10.1.1 (10.10.1.1)  159.507 ms  101.956 ms  95.575 ms

I know that Comcast (formerly AT&T BB) uses the 10-net internally
on their transit networks so they can't just blackhole the stuff.
Insight's ISP is AT&T (now Comcast?). Looking quickly at the AT&T
looking glass, Insight appears to not have its own AS. RFC1918
successfully crossing between ASes would be a Very Bad Thing.
However, it looks like it is completely within AT&T here. Not a
Good Thing, but not the end of the world. For all I know,
10.10.1.1 might be AT&T equipment using their internal 10-net.

> Traceroute -I 10.10.1.1 produces the following:
> 
> traceroute to 10.10.1.1 (10.10.1.1), 30 hops max, 38 byte packets
>  1  10.238.10.1 (10.238.10.1)  29.089 ms  25.387 ms  28.574 ms
>  2  66.56.22.66 (66.56.22.66)  30.923 ms  31.305 ms  33.142 ms
>  3  66.56.22.70 (66.56.22.70)  35.945 ms  35.874 ms  36.832 ms
>  4  c-66-56-23-38.atl.client2.attbi.com (66.56.23.38)  34.740 ms  35.041
> ms  37.537 ms
>  5  12.118.184.41 (12.118.184.41)  41.967 ms  45.584 ms  43.997 ms
>  6  gbr2-p70.attga.ip.att.net (12.123.21.6)  44.988 ms  44.706 ms 
> 43.033 ms
>  7  tbr2-p013602.attga.ip.att.net (12.122.12.37)  49.353 ms  44.010 ms 
> 45.244 ms
>  8  12.122.10.138 (12.122.10.138)  62.244 ms  62.269 ms  62.148 ms
>  9  gbr1-p40.sl9mo.ip.att.net (12.122.11.114)  60.922 ms  67.005 ms 
> 60.264 ms
> 10  gar1-p360.sl9mo.ip.att.net (12.123.24.209)  59.572 ms  64.013 ms 
> 60.198 ms
> 11  12-220-0-69.client.insightBB.com (12.220.0.69)  77.000 ms  76.050
> ms  77.926 ms
> 12  12-220-7-198.client.insightBB.com (12.220.7.198)  95.437 ms  80.068
> ms  84.076 ms
> 13  10.10.1.1 (10.10.1.1)  93.612 ms  97.280 ms  192.994 ms
> 
> 
> 

-- 
Crist J. Clark                               crist.clark at globalstar.com
Globalstar Communications                                (408) 933-4387

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