SIP Third Party IP Phones unregistering to CUCM 11.5

[mukthar786]

 we configured sip third party advance with One DN associated to three or Four Cetis 3500 IP Series Sip Phones

and one user account for Four Phones, from the Cetis SIP Phones is Registered but the CUCM 11.5 side after some time unregistered.

One Question : for four phones need four accounts or one account ok.

[TechLvr]

@mukthar786 
I don’t think using shared lines with 3rd party SIP devices would be a good idea. I suggest you give each device a unique extension, then put them in a hunt group if you want to ring them simultaneously. 

You would also need unique digest credentials for each device. Set the digest username to be the same value as the extension of the device. 

[Jonathan Schulenberg]

DNs absolutely can be shared across multiple 3rd-party SIP phones. I would configure a unique End User per-3rd party device though.

[mukthar786]

Associating Multiple SIP Third party Phones to DN write.

[Ben Petroff]

Did you check the application event log in RTMT to see why the phone lost its registration status in CUCM?

I agree that I would set up one user account per device, but I'm not sure if that would make a difference either way.