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?
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 path to destination are 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 traceroute doesn't. 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 protocols (Tracert standard) Regards, 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 Friday 09 May 2003 06:56, Fabio De Francesco wrote:
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 path to destination are 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 traceroute doesn't. 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 protocols (Tracert standard) Regards, Fabio De Francesco.
On Friday 09 May 2003 07:39, Fabio De Francesco wrote:
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'.
I was under the distinct impression that machines didn't send ICMP error messages about ICMP packets.
Some routers blocks UDP
That would break a significant portion of the internet.
On Friday 09 May 2003 08:09, Anders Johansson wrote:
On Friday 09 May 2003 07:39, Fabio De Francesco wrote:
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'.
I was under the distinct impression that machines didn't send ICMP error messages about ICMP packets.
You know that ICMP echo reply are solicited by ICMP echo request.
Some routers blocks UDP
That would break a significant portion of the internet.
I intended to say UDP with Time To Live set to '0'. Fabio
Fabio De Francesco
On Friday 09 May 2003 08:09, Anders Johansson wrote:
That would break a significant portion of the internet.
I intended to say UDP with Time To Live set to '0'.
That is still damaging as any router loops etc would cause any UDP packets you send to end up in /dev/null without you getting any indication.
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.
-- Check the headers for your unsubscription address For additional commands send e-mail to suse-linux-e-help@suse.com Also check the archives at http://lists.suse.com Please read the FAQs: suse-linux-e-faq@suse.com
__________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com
On Friday 09 May 2003 00:39, Fabio De Francesco wrote:
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
Really appreciate the response. I'll google for the patch you mentioned.
Never heard tracert/traceroute may use udp ...
Tracert
Determines the path taken to a destination by sending
Internet Control Message Protocol (ICMP) Echo Request
messages to the destination with incrementally
increasing Time to Live (TTL) field values. The path
displayed is the list of near-side router interfaces
of the routers in the path between a source host and a
destination. The near-side interface is the interface
of the router that is closest to the sending host in
the path. Used without parameters, tracert displays
help
http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechn...
The most well-known uses of ICMP are the ping and
traceroute (tracert in Window) commands. The ping
command sends out a special ICMP echo request message
to a destination. If the destination is alive, it will
respond with the ICMP echo replay message. This is a
fundamental tool used in network troubleshooting, as
described in Section 67. Handy Unix Network
Troubleshooting Commands.
Traceroute uses the Timestamp services of ICMP to
perform its task of tracing a route to a destination.
The Timestamp message and Timestamp Reply measure the
round trip time that is taken to go from the source to
the destination. Traceroute lists the path and the
round trip time to each router, taken from the source
to the destination. An example of traceroute is
described in Section 67.
http://www.thelinuxreview.com/howto/intro_to_networking/c7632.htm
Martin
.
--- Fabio De Francesco
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
On Wednesday 30 April 2003 12:52, Michael Satterwhite wrote: 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 path to destination are 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 traceroute doesn't. 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 protocols (Tracert standard) Regards, Fabio De Francesco.
-- Check the headers for your unsubscription address For additional commands send e-mail to suse-linux-e-help@suse.com Also check the archives at http://lists.suse.com Please read the FAQs: suse-linux-e-faq@suse.com
__________________________________ Do you Yahoo!? The New Yahoo! Search - Faster. Easier. Bingo. http://search.yahoo.com
participants (5)
-
Anders Johansson -
Fabio De Francesco -
Graham Murray -
Martin -
Michael Satterwhite