[asterisk-users] 1 way audio but audio+video is fine

Brian Wilson brian at wildsong.biz
Thu Jul 14 16:42:29 CDT 2016

Sporadically we get 1 way audio when one party is outside our firewall.

The caller is on NAT, and it works fine most of the time. Caller can hear
the called party, same thing going the other direction. Caller can hear
called party.

Asterisk 13.9 on Debian
chan_sip with  two identical Grandstream GXV3240 SIP phones

In the CLI, I can see calls on our PBX running media on port 5004 when the
call is audio only. When the caller switches to video calls it opens ports
5004 and 5006 and everything works fine.

This does not make sense to me. It seems like audio on port 5004 should
fail either way -- adding another media channel for video should not affect

I believe I have UDP ports 5000-40000 open right now on the firewall.

I also don't understand why it varies from day to day.

Any ideas on how to debug or what might be happening?

Brian Wilson, GISP
Wildsong: 707-827-0001
Mobile: 707-332-3521
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