all ipphone can't call out ,and we found that the register is all fail .
no alarm ,from the signaling we got from site ,when ipphone start to register ,no response from U1980 .
1.check the status of U1980 ,it was running well .
2.check the network between ipphone and U1980 ,it's ok .
ask customer what happyed this morning ,customer said they modify some port in firewall ,which just between the ipphone and U1980 ,after check the firewall ,we found that the port 5060 is forbidden .open the port ,all register restore.
only 2 reason can cause the issue
U1980 is down.
5060 is the default port for sip call ,can't forbidden .