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OpenVPN SIP RTP problem

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fvonderhoeh:
Hi,

I'm using the OPNsense with OpenVPN, which works fine until now. We started using Softphones because of the corona virus and I get some issues:
Outgoing call: The called can here me, but I can not hear him.
Incoming call: The called can here me and I can hear him.

I made some tests and found out following by packet capture on the OPNsense:
On a outgoing call the RTP packets the VPN clients sends the outgoing packets through the tunnel, but the incoming packets are not sent through the VPN tunnel, but to the WAN interface.
On the incoming call the outgoing and incoming RTP packets are send through the tunnel as aspected.

I also checked the States Dump and filtered by the VPN client and RTP port and recognized, that the arrow for source -> router -> destination is different:

Outgoing call:
Int    Proto    Source -> Router -> Destination    State
all    udp    10.10.11.38:30000 -> 192.168.252.3:5004    MULTIPLE:MULTIPLE    
all    udp    192.168.252.3:5004 <- 10.10.11.38:30000    MULTIPLE:MULTIPLE

Incoming call:
Int    Proto    Source -> Router -> Destination    State
all    udp    10.10.11.38:30000 <- 192.168.252.3:5004    MULTIPLE:MULTIPLE    
all    udp    192.168.252.3:5004 <- 10.10.11.38:30000    MULTIPLE:MULTIPLE
(See images attached)

VPN Client is 10.10.11.38
Telephone system is 192.168.252.3

After an incoming call, the outgoing call works fine too, until an undefined time. Sometimes it happens, that I can't hear the called anymore.

System informations: OPNsense 19.7.8-amd64 on a APU2 board.

Is there anything that I can check, or shall I open an issue on github?

Thanks,
Freddy

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