One way Audio on second call - draytek vigor 2860 router


I have noticed that when i call in from VPN the call works okay. If another call is in progress then there is no audio on second call. All calls ring and then no answer so i assume it is the NAT issue on freepbx.

do I need to open firewall ports on VPN?

any pointers on NAT and freepbx and draytek 2860 vigor.

sip_alg is disabled
priority is given to sip
no menu option for VOIP.

have been reading forums all over the place and checked NAT on extension which was set to NO
set to YES and now have some success - further testing.

Not seen the phone NAT mentioned before… but then I’m not a seasoned warrior…

Hope this helps others

more testing…

also eventually found that settings->advanced settings-> dial plan had timeout of 15 seconds on default so mobile got 1 -2 rings and terminated call.

hope this helps someone

also set phone to NAT =Yes and enabled rport on phones to forward to outside lines

at present no external extensions so that should protect security.