Weird VIA in SIP header using 3CX SBC --> 3CX PBX

[thomaspatterns1p]

Hello All,

I have a licensed 3CX PBX on premise setup and working. ( V15 enterprise ) I have the 3CX SBC setup on a remote lan. The phones on the remote LAN register to the local SBC, which has static NAT setup and connects to the remote PBX. Everything works fine, there is no signalling or PBX issues. Upon inspecting the actual packet capture we noticed something on the SIP message header. In the VIA it has seemingly automatically replaced the external SIP server with 127.0.0.1. I reinstalled the PBX just to be sure, and this configuration option never appeared to be prompted, is not selectable under any network/pbx/parameter setting within the PBX itself ( 3CX administrative GUI )

Attached is a snapshot of the wireshark capture, where the SBC responded back to to the original sip invite. 192.168.41.215 is the internal IP of the sip server.

Is this completely normal behavior? Or did I miss some abstract configuration setting?

if anymore information is needed let me know

thank you

 

[leejor]

I'm thinking that because your router is set to forward port 5090 to the local IP of the 3CX server, the local IP is not necessary in the header. Messages are probably "seen" as being "internal" as they pass through the tunnel.

 

[YiannisH_3CX]

Hello @thomaspatterns1p

Please note that this is completely normal as the tunnel service is bound to the localhost (127.0.0.1). As you can see the second VIA and record route point to the correct IP.