From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Fri Aug 12 2005 - 02:54:05 GMT-3
Try playing around with the command below on the router that isn't
responding to all of the traceroute packets:
Rack3R1(config)#ip icmp rate-limit unreachable ?
<1-4294967295> Once per milliseconds
DF code 4, fragmentation needed and DF set
This should help answer your question.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
gladston@br.ibm.com
Sent: Thursday, August 11, 2005 6:59 PM
To: ccielab@groupstudy.com
Subject: Traceroute
Trying to understand these results. Any help appreciated.
Rack2R6#trac 148.5.135.13 (serial of bb2)
Type escape sequence to abort.
Tracing the route to 148.5.135.13
1 148.5.226.2 4 msec 4 msec 4 msec
2 148.5.235.5 16 msec 16 msec 16 msec
3 *
148.5.135.13 24 msec *
Isn't that * on third line strange?
Debug ip icmp on bb2:
.Feb 28 21:21:57: ICMP: time exceeded rcvd from 148.5.235.5
.Feb 28 21:21:57: ICMP: time exceeded rcvd from 148.5.235.5 *
I expected something like this:
Rack2R6#tra 150.100.1.254
1 148.5.146.4 4 msec
2 148.5.14.1 20 msec
3 150.100.1.254 24 msec
Testing trace to loopback of bb2:
Rack2R6#trac 148.5.13.1
Type escape sequence to abort.
Tracing the route to 148.5.13.1
1 148.5.226.2 0 msec 0 msec 4 msec
2 148.5.235.5 16 msec 16 msec 16 msec
3 148.5.135.13 24 msec * *
Just one probe does not change the result:
Rack2R6#trace
Protocol [ip]:
Target IP address: 148.5.135.13
Source address:
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]: 1
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 148.5.135.13
1 148.5.226.2 4 msec
2 148.5.235.5 96 msec
3 *
4 148.5.135.13 24 msec
Doing a little more tests on traceroute, I noticed that repeated
behavior:
When the router is on the path (r5 on the test) it answers with 3 port
unreachable.
Rack2R3#trace 148.5.2.1
1 148.5.235.5 12 msec 12 msec 8 msec <---------- three RTT reported
2 148.5.235.2 24 msec * 20 msec
Rack2R5#deb ip icmp
.Feb 28 22:20:56: ICMP: time exceeded (time to live) sent to 148.5.235.3
(dest was 148.5.2.1)
.Feb 28 22:20:56: ICMP: time exceeded (time to live) sent to 148.5.235.3
(dest was 148.5.2.1)
.Feb 28 22:20:56: ICMP: time exceeded (time to live) sent to 148.5.235.3
(dest was 148.5.2.1)
When the router is the end, is answers only 2 port unreachable:
Rack2R3#trace 148.5.5.1
1 148.5.235.5 12 msec * 8 msec <------------- one RTT is
missed
Rack2R5#
.Feb 28 22:22:33: ICMP: dst (148.5.5.1) port unreachable sent to
148.5.235.3
.Feb 28 22:22:36: ICMP: dst (148.5.5.1) port unreachable sent to
148.5.235.3
Do you know the reason the router just answer two packets?
This archive was generated by hypermail 2.1.4 : Sun Sep 04 2005 - 17:01:19 GMT-3