Using AsteriskNOW/FreePBX 13 with a Mock Cellular Network

I am trying to set up a mock cellular network that simulates VoLTE by utilizing AsteriskNow as the SIP server.

Here is my current setup:

  1. I am using an Agilent E6621A PXT Wireless Communications Test Set, which supports wireless LTE connections to any smartphone with the right configuration. This allows me to create a mock cellular network. This test set has an IP address of, and gives the smartphone an IP address of and/or depending on the setup.
  2. By setting the P-CSCF of one of the bearers of the network setup on the instrument to the address of a SIP server, I can have the UE, or cellphone, connect to that server to provide a given set of services, such as SIP.
  3. I am using an LG G3 VS985 and a iPhone 6S+, both of which support SIP when in VoLTE mode.

I am using FreePBX which utilizes Asterisk 13.12.1 and I have been able to get multiple desktop clients connected and calling successfully.

The problem I am having, however, is that although the UEs that I am testing send a “REGISTER” request to, the local IP of our Asterisk/FreePBX Server, we get no response to the REGISTER message. I have also tested pinging between the two destinations and found that the pings and their responses are timing out.

Does anyone have any idea as to what the problem is? It seems to possibly be a network problem possibly caused by our router (which is a Cisco ASA5505 running the most recent version of its firmware). Note that the Server and PXT are connected to the same hub, which means all packets can be seen by all computers. Any and all recommendations are greatly appreciated. I can also provide a Wireshark capture of this issue should anyone need more details on the issue. Also let me know if you need more details on what I am using or what I am doing.