Troubleshooting not able to make VoIP calls with wireshark

03/26/2020 52 13108

DESCRIPTION:
Troubleshooting not able to make VoIP calls with wireshark

RESOLUTION:

Problem

Clients behind the Sonicwall are not able to make VoIP calls

Troubleshooting

1. Run a packet capture on the Sonicwall and monitor for the source IP address and the destination IP address for the VoIP call.
2. Export the packet capture as a Libpcap file as shown in the screen shot below.



3. Run the pcap extension file downloaded in Wireshark.

4. The screenshot below shows what a successful call setup and teardown should look like in Wireshark.



To inspect the traffic flow for a call set up, select VoIP Calls from the Telephony menu, choose a call and click on Flow.

5.The screenshot below shows a typical SIP-initiated conversation.



Calls can fail for the most obscure reasons.For example, some SIP gateways might expect some of the call
setup information in one format, while another part of the SIP infrastructure provides it in a different one.

6. The screenshot below shows a SIP invite request packet.



Within the header, the Allow property is displayed, in this case with all elements on one line. But if another part of the 
infrastructure expects them as different elements, the call might fail. The most practical way you can troubleshoot
this type of problem is by inspecting the packets in Wireshark to figure out the issue with the SIP call.

7. To search for SIP error codes in a Wireshark capture enter the following filter: sip.Status-Code >= 400




For a detailed explanation of SIP Code errors click here.