Tracing a UDP Route

If you are experiencing connectivity problems and suspect a firewall issue, mtping can trace the route that packets are following to isolate where your data is being blocked.

By adding the -t option, mtping will behave much like the unix traceroute utility, except that mtping sends actual MTP datagrams.  Firewalls which are blocking MTP traffic on the selected port can be identified by the point where the trace stops receiving responses.

Below is an example trace which suggests a router near mtping may be blocking MTP on port 8080:

host-3: mtping -t ACT_PING ( 1 1ms "TTL Exceeded" 2 3ms "TTL Exceeded" 3 * 6000ms "No Response" 4 * 6000ms "No Response" ^C

Next is an example trace showing that no MTP application is running on port 8081 of the given machine:

host-4: mtping -t ACT_PING ( 1 9ms "TTL Exceeded" 2 8ms "TTL Exceeded" 3 9ms "TTL Exceeded" 4 13ms "TTL Exceeded" 5 177ms "TTL Exceeded" 6 154ms "TTL Exceeded" 7 14ms "TTL Exceeded" 8 16ms "TTL Exceeded" 9 13ms "TTL Exceeded" 10 23ms "TTL Exceeded" 11 80ms "TTL Exceeded" 12 54ms "TTL Exceeded" 13 102ms "TTL Exceeded" 14 55ms "TTL Exceeded" 15 88ms "TTL Exceeded" 16 79ms "Unreachable: No Application on that Port" 17 62ms "Unreachable: No Application on that Port" ^C

Not all systems will send or receive the "Unreachable" message.  Therefore it may not be clear from mtping's output whether a firewall is blocking access near the server or no server is running.