Ethereal-users: Re: [Ethereal-users] Wierdness in CablemodemLand?

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From: Guy Harris <gharris@xxxxxxxxx>
Date: Mon, 22 Apr 2002 00:16:53 -0700
On Sun, Apr 21, 2002 at 10:12:07PM -0700, John E. Mayorga wrote:
> traceroute to 24.127.52.9 (24.127.52.9), 3 hops max,
> 38 byte packets
>  1  c-24-127-52-1.we.client2.attbi.com (24.127.52.1) 
> 9.447 ms  11.929 ms  10.144 ms
>  2  c-24-127-52-9.we.client2.attbi.com (24.127.52.9) 
> 17.247 ms  19.768 ms  21.184 ms
> 
> traceroute to 24.127.52.10 (24.127.52.10), 3 hops max,
> 38 byte packets
>  1  c-24-127-52-10.we.client2.attbi.com (24.127.52.10)
>  0.082 ms  0.065 ms  0.019 ms

Well, that's some machine that's on the same subnet, as far as IP is
concerned.

Is it your machine?

What does the routing table look like on your machine?

> traceroute to 24.127.52.14 (24.127.52.14), 3 hops max,
> 38 byte packets
>  1  c-24-127-52-1.we.client2.attbi.com (24.127.52.1) 
> 8.609 ms  7.837 ms  7.974 ms
>  2  c-24-127-52-14.we.client2.attbi.com (24.127.52.14)
>  25.201 ms  17.533 ms  19.855 ms
> 
> traceroute to 24.127.52.15 (24.127.52.15), 3 hops max,
> 38 byte packets
>  1  c-24-127-52-10.we.client2.attbi.com (24.127.52.10)
>  2990.854 ms !H  2999.486 ms !H  2999.919 ms !H

> Subquestion - Why is it that when the script gets to
> 24.127.52.15,19,26,28, etc. the connection does not go
> through the router?

Well, it's apparently trying to go through *some* machine.

Unfortunately, that machine can't get to 24.127.52.15 - 24.127.52.10 is
returning a Host Unreachable.

> I used pretty much the same script for ARPing 1.04.
> Here is the output (which makes sense):
> 
> ARPING 24.127.52.1 from 24.127.52.10 eth0
> Unicast reply from 24.127.52.1 [00:B0:8E:F7:3C:54] 
> 8.803ms
> Sent 1 probes (1 broadcast(s))
> Received 1 response(s)

OK, so I infer from "from 24.127.52.10" that 24.127.52.10 is your
machine.

The question is whether it has something in its routing table to tell it
that it's its own router to some machines (machines it can't, in fact,
get to).