help meaning traceroute

[Luca Rasconi]

[h3mih120]/# traceroute h3mih047
traceroute to h3mih047.domain.it (10.213.129.7), 30 hops max, 20 byte packets
1 10.213.35.250 (10.213.35.250) 0 ms 0 ms 0 ms
2 h3mih047.domain.it (10.213.129.7) 0 ms 0 ms 0 ms
3 * * *
4 * * *

Seems traceroute reach the host, but why after point 2, where the host was reached, are the atseriscs??
In fact i'm not able to ping the host.

Thank you
Luca

[Robert-Jan Goossens · Accepted solution]

Hi Luca,

10.213.35.250 is the default router for your own server
so that's the first, the second is the server you are looking for.

Kind regards,

Robert-Jan.

[Luca Rasconi]

Thank you, but what is the meaning of the asterisc after the point 2?


Luca

[jim bidebo]

hmm, you shouldnt have any asteriscs after point 2 since you reached your target at point 2.

otherwize when it shows asteriscs it means that it routes throu a mashine that doesnt "support" ICMP i belive, im not 100% sure thou.

[Ron Kinner]

Traceroute has two modes of operation. The first mode expects a TTL expired message back from each step on the way to the host. However, once the packet reaches the host the host sees no reason to complain about the TTL being expired since it won't be forwarding it so a second mechanism is used where an attempt is made to reach a high numbered port which we assume is not in use so that we will get a port not available message from the host. Traceroute then stops.

However, in your case, it appears that the host h3mih047 may have actually sent back a TTL expired message instead of a port unreachable message. Thus there was nothing to tell the traceroute that it had reached its goal. Perhaps the port is in service?
netstat -nr
will show what ports are in use if you have access to h3mih047. You can change the port to a different one and see if that makes a difference. Usually the high port number is 33434 but you can change it to say 33500 with

traceroute -p 33500 h3mih047

If it still doesn't work, I think the problem lies with h3mih047 which is not responding as expected. (I assume your traceroute works to other destinations?)

Ron

[Ron Kinner]

Oops should have been netstat -an

Ron

[Luca Rasconi]

yes,ok. I supposed :-)

bye
Luca