the network problem lead to sometimes fax failed.

Requrie customer check the problem with network.

after customer repaire the network problem, the fax proble solved.

1. trace sip signalling on IAD by command "trace all". from the signalling we know the signalling is all right. the negotiate of fax mode is successful. so we need to make network captures to analysis this problem.
2. Get the network capture, we can see in the abnormal fax, IAD 208 didn't reveive any RTP stream. that is why the fax failed.



3. ping from IAD to the other side, the result as blew, so we see the network cannot be connected, that is why there is no any RTP stream:
TERMINAL#ping 172.XX.XX.2
{ <cr>|-c<K>|-d<K>|-t<K>|-q<K>|-i<K>|-s<K>|-v<K> }:

Command:
        ping 172.XX.XX.2
  PING 172.XX.XX.2: 56  data bytes, press CTRL_C to break
  Request time out
  Request time out
  Request time out
  Request time out
  Request time out

Getting the network captures is the most effective way to analysis the problem of fax.