Allowing Remote Worker to Use VoIP PBX via VPN

Question

Hi All - 
 I currently have a VoIP PBX on a separate VoIP LAN in our office (192.168.25.X). The PBX is allowed to communicate via SIP to our SIP Trunk Service Provider. I didn't need to make any special SIP configs (Network Protection --> VoIP) in this setup. 
 I need to allow a few remote workers connect to the PBX. I've tried creating both SSL VPN's and L2TP VPN's and creating firewall rules to allow traffic to pass to and from the VPN networks and the internal VoIP network (192.168.25.x). It appears to work at first, the phone rings in both directions, but there is no audio in either direction. 
 What am I missing? 
 Scott

rsenio · Accepted Answer

First of all, can your PBX communicate with the VPN subnet? So from your x.25 subnet can you pass traffic to the VPN subnet? 
 Without knowing what type of PBX and VOIP you use.... 
 If your PBX is an Asterisk flavor it probably has the option localnet=192.168.25.0/255.255.255.0 specified somewhere in one of your SIP config files (sip_general_additional.conf?) 
 You'll need to add another line for your VPN subnet (added to sip_general_custom.conf?) and restart your PBX. 
 If this doesn't fix your issue, you'll need to check your PBX and post on those forums instead of the Sophos ones. This isn't the place