Hi,

I have two FS's (FS1, FS2) with ZRTP enable in two sites.

I can make end-to-end ZRTP calls between two CSipSimple/ZRTP clients over the two FS's bridge where both FS's are set to 'proxy_media=true'.

CSipSimple -> FS1 ---Internet -à FS2 -> CSipSimple.

Now I connected a PBX to each FS with SIP-Trunk.

PBX -> FS1 ------- FS2 -> PBX.

When calling locally from CSipSimple to a PBX extension on the same FS then the ZRTP is terminated by the FS as MITM which is OK (FS dialplan 'proxy_media=false').

What I cannot figure out is how to terminate ZRTP call between CSipSimple/FS1 and FS2/PBX.ext and vice versa.

CSipSimple -> FS1 ------- FS2 -> PBX.ext.

I've tried to setup:

FS1 with 'proxy_media=true' (passthrough ZRTP)  +   FS2 with 'proxy_media=false' (terminate ZRTP).

OR

FS1 and FS2 with 'proxy_media=false' .

All results with ' ZRTP not negotiated on both sides; disabling ZRTP passthru mode'.

Any help will be appreciated.

Regards

Assaf