From: oherrera (oherrera@Prodigy.Net.mx)
Date: Mon Apr 07 2003 - 19:52:02 EDT
Mh... The original IP Header + 64 bits of data is included
in the ICMP Time Exceeded Message...
If we assume that our address is a.a.a.a and target is
t.t.t.t then the IP header in all ICMP Time Exceeded Message
should read:
from a.a.a.a to t.t.t.t, but... if there is some proxy
inside whose internal address is b.b.b.b the IP header would
change and any device between b.b.b.b and t.t.t.t where the
packet expires would include and IP header inside the ICMP
Time Exceeded Message reading: from b.b.b.b to t.t.t.t,
wouldn't it?
Now, assuming this proxy has an external IP address of
e.e.e.e (which a.a.a.a can see) and somehow, this proxy just
redirects traffic for a certain port to t.t.t.t on the
internal network, in theory, you would receive ICMP Type 11
:
[IP from e.e.e.e to a.a.a.a]....[ IP inside ICMP protocol:
from a.a.a.a to e.e.e.e?]
if expiring before and on the proxy... and you might
receive:
[IP from e.e.e.e to a.a.a.a]....[ IP inside ICMP protocol:
from b.b.b.b to t.t.t.t?] if expiring after the proxy (on
the internal network.)
I haven't actually tried this but looks like it would work
for mapping an internal network behind a proxy under some
circumstances (using a sniffer at least).
But regarding the question being posted, I would have
another question... Do any traceroute implementation favours
IP header inside the ICMP type 11 protocol over the IP
header of the packet itself under some circumstances?
Omar Herrera
> Hi all,
>
> While trying to do traceroute on one of the server i get
> the following reply:
>
> $traceroute a.b.c.d
> 1 192.168.0.254 (192.168.0.254) 0.442 ms 0.397 ms
> 0.358 ms
> 2 62.150.42.1 (62.150.42.1) 1.951 ms 1.315 ms 1.249
> ms
> 3 172.17.8.149 (172.17.8.149) 43.577 ms 23.481 ms
> 17.653 ms
> 4 border.qualitynet.net (195.226.227.1) 19.935 ms
> 20.902 ms 21.896 ms
> 5 isp.qualitynet.net (195.226.227.10) 19.928 ms 23.302
> ms 21.839 ms
> 6 192.168.226.38 (192.168.226.38) 71.321 ms 282.457 ms
> *
> My Question is why I am getting 192.168.226.38 non-route
> able address output in traceroute reply? As far as i think
> these private address space is not route able on the
> internet.
> Any sugestions?
>
> Vineet
>
>
> [Attachment: signature.asc]
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