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Old 09-14-2010, 04:00 AM   #1
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Registered: Jun 2010
Location: Texas
Distribution: Ubuntu, Puppy, Helix, Backtrack, RedHat, Slackware
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tcpdump help, please!

I'm looking at a tcpdump output. It's shows a UDP port scan. I got that much, and it's the important part. I still can't figure out one thing.

15:58:52.007004 IP > icmp 36: udp port 33322 unreachable

15:58:52.007013 IP > icmp 36: udp port 33736 unreachable
...and so on, and so on, with different ports. Obviously a UDP port scan. What I can't figure out, for the life of me, is: what is "icmp 36:" supposed to mean? I can't figure out the 36. I initially thought it was type and code, but type and code for port unreachable would be 33. I know that I should know this, and I'm thinking it is something obvious and incredibly simple, but it's driving me crazy. Please help!
Old 09-14-2010, 09:07 PM   #2
Registered: Aug 2007
Location: Vietnam
Distribution: RedHat based, Debian based, Slackware, Gentoo
Posts: 724

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What exactly tcpdump command did you use? About of '36', I guess it is length of icmp message. Try to write the raw packets to a file (-w) and open it with Wireshark for more details.


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