I currently have successful two way calls (signalling and media) in the following setup

External Linphone --> Freeswitch --> Freeswitch SBC -> Router -> Kamailio --> Internal Linphone

However, when I try to call a Cisco handset that is registered to CUCM9 via CME in the following config:

External Linphone --> Freeswitch --> Freeswitch SBC -> Router -> CME -> CUCM9 --> Cisco handset

The call signalling appears to be working fine and I can successfully initiate a call from each end, but the only RTP stream that is working is from the external Linphone client to the Cisco handset.

Note that CME is being used as a CUBE device, so all SIP and RTP goes via it.

Looking at the RTP debugs on CME I can see the problem is that the "Media Dest Addr" is getting set to the external side of the FS SBC rather than the internal IP address.

I tried setting adding:

<action application="set" data="disable_rtp_auto_adjust="true" />

to the dialplan on the SBC, but it made no difference.

Any suggestions as to what to check next?

Thanks

Peter