Cisco Traceroute ICMP Replies

3750-1#traceroute 1.1.1.1

Type escape sequence to abort.

Tracing the route to 1.1.1.1

  1 10.10.10.1 8 msec 0 msec 0 msec

  2 10.11.11.2 0 msec 0 msec 0 msec

  3 10.11.11.2 !A  *  !A

The above is a sample traceroute of what you might have already seen. It was definitely something I came across and thought I would just jot down for future reference.  This is good for trouble shooting and understanding where the packet is actually going. 

        When doing ICMP variables like ping and traceroute its good to know the characters and functions behind what they actually mean; it helps with troubleshooting. Below is a table of these characters from Cisco.

*                      The probe timed out

A                       Administratively prohibited (example, access-list)

Q                      Source quench (destination too busy)

I                       User interrupted test

U                       Port unreachable

H                       Host unreachable

N                       Network unreachable

P                       Protocol Unreachable

T                       Timeout

?                       Unknown packet type