Question:

When does the N510 sends Registration request with expires = 0. This means a SIP de-registration.

Answer:

There are different scenarios that an N510 sends a de-registration request.

1. Web-interface: Uncheck "Active" option for this SIP account
2. Web-interface: Delete SIP account.
3. Device expects SIP values are no longer valid:

   1. address of record ( "displayname"<sip:user-id@domain.net> )

   2. contact addresses ( e.g. user-id@97.98.96.1:53260 ) on the registration server (location database)

De-registration is started with possible new registration

So initiations for de-register procedures are:

• address-of-record was modified ( displayname, user-id, login-id, domain )
• contact address might have changed:
• new local sip port
• new local IP address
• new public IP address (detected by STUN) (checked any 240s, configurable)
• new public port ( not checked periodically )

Possible solution:

Disable / delete the STUN settings in the device.

Upgrade device to software >211 because of STUN improvement to avoid these issues.