05-01-2008 05:38 AM - edited 03-03-2019 09:47 PM
Im troubleshooting an issue within my network.
I can ping a destination within my router
but I can not trace to it.
My trace just fails along the path
I was under the impression that
both trace and ping use ICMP packets?
05-01-2008 06:47 AM
that is correct both use ICMP, but differ in ICMP types.
http://iptables-tutorial.frozentux.net/chunkyhtml/a6339.html
U might have an ACL, or if in MPLS network have traceroute disabled ( best practice).
HTH
Sam
05-01-2008 07:14 AM
Hi,
Just an additional comment: Cisco routers will use UDP packets for the traceroute. Only the "TTL expired in transit" answer is ICMP. You can see this from an extended traceroute:
R1#traceroute
Protocol [ip]:
Target IP address: 1.1.1.1
Source address:
Numeric display [n]:
Timeout in seconds [3]:
Probe count [3]:
Minimum Time to Live [1]:
Maximum Time to Live [30]:
Port Number [33434]: <-------- UDP port 33434
Loose, Strict, Record, Timestamp, Verbose[none]:
Type escape sequence to abort.
Tracing the route to 1.1.1.1
The first packet will be sent to UDP port 33434 and each subsequent packet will have the UDP port number increased by one (33435, 33436, ...). In case your traceroute starts from a router, do not block those UDP packets and also allow the ICMP TTL expired packets in return, as described in the previous post.
Hope this helps! Please use the rating system.
Regards, Martin
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide