Choppy lines on server behind firewall

Good day,
We recently move our PBX Server behind firewall thats the time we encountered choppy lines. Is the firewall something to do with this?


Help will be much appreciated.


if you’re using sip trunks, try changing the registration port if your supplier supports it. A lot of routers/firewalls will try to be helpful with SIP traffic but it can have unexpected results.
What sort of firewall are you using?

(btw - love the decnet tag)

Nelly - The audio is transmitted in RTP not SIP. Changing the signaling port will not alter the media stream.

I would look for mismatched interfaces on the firewall that are dropping packets.

A lot of firewalls need several things to make SIP work smoothly adjusting UDP timeout, disabling SIP ALG, the more expensive the firewall quite often the more settings there are to consider :slight_smile:

E.G. On a sonicwall there’s a few things to modify like SIP transformations and enabling consistent NAT

Again, I must jump in an increase my emphasis SIP does not participate in the media stream SIP is a signaling protocol. Media is transported via RTP.

If you are getting audio artifacts packets are either being lost, delayed or arriving out of order. Any type of packet loss on an interface would cause these audio issues. Look for CRC’s, frame errors etc. Then fix the bad jumper, connection, interface or whatever the problem turns out to be.