Phones keep sending audio to external Asterisk server IP

Recently set up some phones at a site with MPLS connection. We need our phones to connect to the internal IP of our Asterisk box, but phone configs keep reverting to the external IP.

When doing packet captures with Wireshark, we see RTP traffic going from the phone to the external sever IP - and RTP traffic from internal IP of the server, traveling back to the phone.

Where is the server IP configured within Asterisk? I must not be finding the right spot…

In many cases, it isn’t explicitly configured within Asterisk. For STUNless NAT, you may need to set externip or externhost in sip.conf.

You should also look at the setting of canreinvite.

Thanks for the reply.

Since we are going over MPLS, NO NAT should be happening whatsoever.

If it isn’t defined explicitly, how does it know where to send the RTP?

I’m not familiar with MPLS.

The recipient of the RTP tells the sender where to send to. In default of reinvites or NAT, this will be address of the interface over which it is sending the SIP message.