When you try to register with the same SIP account on a second IP Phone, the first IP Phone registered does not log out automatically and doesn’t display anything related to this, although in the SIP Server PBX system, the first IP Phone is not registered with it’s IP for the specific account, the second one is. All the calls to that account will be passed to the second IP Phone. And also the first IP Phone cannot make any calls.
1. Unregister the second IP Phone and check the SIP account table on the PBX.
2. Look-up IP Phones timers for login expire and calculate ½ of this time since the IP Phone is in stand by state because then the IP Phone will send a Register message to the PBX.
3. Check SIP account table on the PBX again.
4. Be aware of the parameters discussed at point 2.
5. Check the PBX feature to disable multiple terminals to register with the same SIP account.
1. Check display of the IP Phone. R: Seems to be registered
2. Can you make a call? R: NO
3. Can you receive a call? R: NO. The call is received by another IP Phone.
4. Check the SIP account table of the PBX and the corresponding IPs
5. Check the IP Phones timers
If one of your IP Phone is not receiving or sending calls any more, although it seems to be registered on the display, always check the PBX table for registered accounts and look-up the IP corresponding to that account. Another IP Phone can be registered with the same account.
Some PBX systems have a feature to not allow multiple IP Phones to login with the same account.
Please see attached for a clear picture of the scenario.