This is a fairly complex setup.
3CX has an LAN space of 10.0.x.x and a default gateway heading out to our public space in the 67.x.x.x IP-space which works fine across the dozen trunks we have (all of the trunks are internet-based). We ordered a new AT&T SIP trunk which is a private circuit -- NOT internet based -- it was delivered on a new circuit and has their own router to handle SIP traffic.
The AT&T traffic must terminate calls to 12.194.x.x IP space, which can only be reached through the AT&T router (which has a 32.x.x.x MPLS IP) -- we have static routes built and L3 connectivity validates end-to-end.
Here are our test results:
Outbound calls = work perfect, no issues.
Inbound calls = disconnect after 30s.
Troubleshooting:
The PCAP shows that the inbound call is received and call setup completes without incident. What we are seeing is the 200 OK message is never ACK'd because it is sending to the 12.194.x.x a contact header public IP off of 3CX WAN (67.x.x.x) and not the 32.x.x.x IP address and the 12.194.x.x cannot reach the 67.x.x.x IP address because it is a private circuit....
We need to modify the INBOUND parameters of the contact host part to be the 32.x.x.x IP address.
I have added the IP into SIP Trunk | Inbound Parameters | Contact: Host Part, custom field, 32.x.x.x:5060
* AND *
Also added the IP into the SIP Trunk | Outbound Parameters | Contact: Host Part, custom field, 32.x.x.x:5060
* AND *
Added into SIP Trunk | Options | Select which IP address to use in 'Contact' (SIP) and 'Connection' (SDP) fields, use this IP address, 32.x.x.x
After all of these settings have been set, 3CX is still sending the 67.x.x.x IP in the contact host part....
3CX has an LAN space of 10.0.x.x and a default gateway heading out to our public space in the 67.x.x.x IP-space which works fine across the dozen trunks we have (all of the trunks are internet-based). We ordered a new AT&T SIP trunk which is a private circuit -- NOT internet based -- it was delivered on a new circuit and has their own router to handle SIP traffic.
The AT&T traffic must terminate calls to 12.194.x.x IP space, which can only be reached through the AT&T router (which has a 32.x.x.x MPLS IP) -- we have static routes built and L3 connectivity validates end-to-end.
Here are our test results:
Outbound calls = work perfect, no issues.
Inbound calls = disconnect after 30s.
Troubleshooting:
The PCAP shows that the inbound call is received and call setup completes without incident. What we are seeing is the 200 OK message is never ACK'd because it is sending to the 12.194.x.x a contact header public IP off of 3CX WAN (67.x.x.x) and not the 32.x.x.x IP address and the 12.194.x.x cannot reach the 67.x.x.x IP address because it is a private circuit....
We need to modify the INBOUND parameters of the contact host part to be the 32.x.x.x IP address.
I have added the IP into SIP Trunk | Inbound Parameters | Contact: Host Part, custom field, 32.x.x.x:5060
* AND *
Also added the IP into the SIP Trunk | Outbound Parameters | Contact: Host Part, custom field, 32.x.x.x:5060
* AND *
Added into SIP Trunk | Options | Select which IP address to use in 'Contact' (SIP) and 'Connection' (SDP) fields, use this IP address, 32.x.x.x
After all of these settings have been set, 3CX is still sending the 67.x.x.x IP in the contact host part....
