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.