traceroute does not respond on one attempt

gojericho0

Reading through some cisco documentation

http://www.cisco.com/en/US/tech/tk364/technologies_tech_note09186a00801ae32a.shtml#ciosr

I noticed that on the 4th hop one of the responses comes up * I thought this was just fluke thing on the response, but noticed when I lab it up it occurs on every other traceroute response only on the last hop.

1 150.1.1.2 4 msec 0 msec 4 msec
2 150.1.2.2 4 msec 4 msec 0 msec
3 150.1.3.2 0 msec 0 msec 4 msec
4 150.1.4.2 4 msec * 0 msec

Can someone explain to me what is causing this and why it happens on every other response on the last hop?

gojericho0

Haha scrolling down i think i found my answer. was very confused there for awhile

If the port is unreachable, type=3, code=3, then the packet is sent back in response to the UDP probe packets when they reach the destination (the UDP application is not defined). These packets are limited to one packet per 500 ms. This explains why the response from the destination (see the outputs for the Cisco router and Linux) failed in the even responses.