I have been struggling to get his working ;
Our Setup is
PSTN terminated on Nortel.SIP Trunk between Nortel and cisco .SNOM SIP Phones terminated on Cisco CME Version 7.1
Cisco IP Phones are also terminated on Cisco CME.
When I enable "RTP Encryption:" on SNOM SIP Phone then voice works one-way
i.e for calls initiated from Snom to Cisco Phones ( both phones are configured on CME )
If calls are initiated from Cisco Phone to Snom Sip Phone then voice works perfectly.
If I disable "RTP Encryption:" then calls from PSTN to SNOM endpoints doesnt work, it rings with no voice.If I press the hold key for 5 sec and release then voice starts working.
What tweak is needed on Cisco CME to get this working.
We got RTP issue too. SNOM IP PHONE didnt work with us, we are testing D-link IP Phones
Encryption is supported only with Cisco phones in SCCP mode.