One sided audio with calls over VPN

We have an asterisk server (v1.8) that is at one site and we have users with phones there which work fine.

We have other users at site B with handsets configured to use the asterisk server at Site A. These register ok but when used one party can’t hear the other party. Sometimes this happens as soon as the call connects, sometimes it happens after a few minutes. It happens for any user at Site B, whether they call users in Site A, or external phone numbers.

So far it only appears to be on calls made over the VPN.

Any ideas what this might be?

We’ve set up another test server between another two sites and I see the same issue.

There’s no packet loss, or networking issue between the sites, and the firewall doesn’t block any traffic over the VPN.


I think I’ve solved it.

The problem looks to have been that the other sites IP address wasn’t listed as a local network in asterisk. I’ve added the other sites subnet and now calls appear to be working fine.