welcome to the Polycom Community.
It is always useful to include the currently used UC Software version as issues experienced or a question asked may already be addressed in a newer release.
This also allows yourself and others to check against current software release notes, Administrator Guides or FAQ post’s.
The above is also stated in the "Must Read First" and is the absolute minimum requirement every new post should include. .
In addition providing us with this basic information gives Polycom an idea what Software Versions are used in the field and avoids wasting time trying to troubleshoot issues which have already been addressed.
Therefore the Polycom VoIP FAQ contains this post here:
Question: How can I find out my SIP or UC Software Version of my Phone?
Resolution: Please check here
To answer your actual question you may want to look at the following Parameter:
The keep-alive interval in seconds. Sets the interval at which phones sends a keep-alive packet to the gateway/NAT device to keep the communication port open so that NAT can continue to function. If Null or 0, the phone does not send out keep-alive messages.
0 - 3600
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services