From: Kenneth Wygand (KWygand@customonline.com)
Date: Fri Sep 05 2003 - 16:45:32 GMT-3
Phuong,
This is because the traceroute command maps based on the receipt of "TTL expired" ICMP packets received from routers at each hop - the last hop responds back with "ICMP Unreachable" messages. These are rate limited by default on the destination router to prevent ICMP storms from a malicious connection.
Use the command "ip icmp rate-limit unreachable 1" on the destination router in global config mode and your problem will go away.
Ken
-----Original Message-----
From: Phuong [mailto:kieu@hn.vnn.vn]
Sent: Fri 9/5/2003 3:33 PM
To: ccielab@groupstudy.com
Cc:
Subject: Strange Traceroute result
Hi All
I often encounter a strange output every time I trace route to a remote
destination.
I always miss one icmp packet in the last hop.
Something likes that
R2#traceroute 150.50.8.8
Type escape sequence to abort.
Tracing the route to 150.50.8.8
1 150.50.123.6 20 msec 20 msec 20 msec
2 150.50.124.7 [AS 600] 20 msec 24 msec 24 msec
3 150.50.78.8 [AS 600] 36 msec * 36 msec
R4#traceroute 150.50.8.8
Type escape sequence to abort.
Tracing the route to 150.50.8.8
1 150.50.123.2 [AS 200] 20 msec 20 msec 20 msec
2 150.50.123.6 [AS 200] 32 msec 36 msec 36 msec
3 150.50.124.7 [AS 600] 40 msec 36 msec 36 msec
4 150.50.78.8 [AS 600] 52 msec * 52 msec
R4#traceroute
Protocol [ip]:
Target IP address: 150.50.8.8
Source address: 150.50.4.4
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
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 150.50.8.8
1 150.50.123.2 [AS 200] 20 msec 20 msec 20 msec
2 150.50.123.6 [AS 200] 36 msec 36 msec 36 msec
3 150.50.124.7 [AS 600] 36 msec 36 msec 36 msec
4 150.50.78.8 [AS 600] 60 msec * 48 msec
Those asterisks always appear (and delay for a while) every time I trace
route, from any router, any source to any destination, and every lab
that I have finished.
My router is all 2500 with 12.2 IOS,
Could anyone explain?
TIA
Phuong
P/s: there is no problem when I trace route from my router to a
destination on Internet.
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