Blocking unauthorized SIP calls to Polycom desk phones

Login to phones web interface.

Create config.cfg file with the following contents

<PHONE_CONFIG><voIpProt.SIP.requestValidation voIpProt.SIP.requestValidation.1.method=”source” voIpProt.SIP.requestValidation.1.request=”INVITE” />
<CONFIG_FILES
/>
</PHONE_CONFIG>

Load config.cfg file under utilities.