IP phone unregistered

[Aadar-Soomro]

Cisco IP phone is in unregistered state after calling. Checked the forward traffic logs all the packets are accepted by firewall. what is the possible cause of IP phone getting unregistered after calls.

[johnathan]

It is doubtful that it is a firewall issue, especially if the phone was able to register in the first place.

I would start by taking a PCAP while you end a phone call to see specifically what is going on to cause the phone to de-register. 

[Aadar-Soomro]

Just asked the VoIP team to investigate at their end. but i am unable to see any issue with FortiGate

[Umer221]

@Aadar-Soomro 

Here is an article to initially troubleshoot the issue:
https://community.fortinet.com/t5/FortiGate/Technical-Tip-VOIP-calls-using-SIP/ta-p/193831

The above article has a list of further articles at the bottom to further investigate the issue.