You always learn something new :), I was curious so I
traced some host out there doing tcpdump -vx host and
I see Linux really sends out udp packet like below.
Some routers can't block udp, they just don't send
icmp ttl expired to the source.
[udp sum ok] udp 40 (ttl 2, id 59934, len 68)
4500 0044 ea1e 0000 0211 c23e
0cd5 bba7
c392 803d fa05 829f 0030 f405
4041 4243
4445 4647 4849 4a4b 4c4d 4e4f
5051 5253
5455 5657 5859 5a5b 5c5d 5e5f
6061 6263
6465 6667
[udp sum ok] udp 40 (ttl 3, id 59935, len 68)
4500 0044 ea1f 0000 0311 c13d
0cd5 bba7
c392 803d fa06 82a0 0030 f403
4041 4243
4445 4647 4849 4a4b 4c4d 4e4f
5051 5253
5455 5657 5859 5a5b 5c5d 5e5f
6061 6263
6465 6667
Martin
--- Fabio De Francesco
Sorry Michael, I was a bit inattentive when I replied to you before. The things are opposite: Traceroute uses UDP protocol, while Tracert uses ICMP echo request. They both elicit the ICMP expired on transit message when TTL goes to '0'. Some routers blocks UDP and doesn't send any ICMP answer to you, that is why tracert works with them. Fabio De Francesco
On Wednesday 30 April 2003 12:52, Michael Satterwhite wrote:
I'm having a problem with traceroute. When I run it (e.g. traceroute weblore.com), it pauses for a bit, then prints out a series of hops with absolutely no information. After a bit, it repeats this. Here's a sample output:
linux:/home/michael # traceroute weblore.com traceroute to weblore.com (198.65.246.22), 30 hops max, 40 byte packets 1 * * * 2 * * * 3 * * * 4 * * * 5 * * * 6 * * *
Is there something I'm missing?
Traceroute obtains '*' when some routers along the
configured to silently drop ICMP request with TTL set to '0'. Tracert uses the UDP protocol to solicitate some response from the same hops, so it's possible that it gets answers while
I know there's a patch on the wild to be applied to traceroute that allows you to choose whether you want to use ICMP or UDP
On Friday 09 May 2003 06:56, Fabio De Francesco wrote: path to destination are traceroute doesn't. protocols (Tracert
standard) Regards, Fabio De Francesco.
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