I have come across a strange problem with our VPN and BCM 50 (Nortel/Avaya) phone system.

As you can tell by my other questions I have been doing some work on setting a VPN up from one location to another and it's all working well. With one exception.

We have an IP phone that is connected at the remote location, straight to a router which has a VPN tunnel to our main practice. The phone works mostly, but every few calls it turns into a one way call. As in, the caller (from the remote phone) can't hear the receiver- but the receiver can hear the caller.

This is fixed by setting the VPN tunnel to be the default route for all traffic.

The problem with fixing it that way is that all traffic then goes through the tunnel which slows internet access etc. down considerably.

The router is set to send the following over the VPN:

192.168.1.0/24
192.168.2.0/24
192.168.4.0/24

The IP of the remote location is:

192.168.3.0/24

The remote router (where the phone is) is a Draytek 2830n, and the local router (at the main practice) is a Draytek 2820.

We are using an IPSec tunnel with AES encryption <- as a result of a previous answer pointing to the incompatibility in the hardware encryption.

Any advice would be appreciated!