Scenario
This article will explain how to identify SIP registration issues using a the built in packet capture function found on most Grandstream devices.
Step 1:
Login to your device and start the packet capture (in this example we will perform a packet capture from a UCM6202):
Step 2:
Initiate a registration request from an IP Phone by either rebooting the phone or; disabling the account, save and apply settings, re-enable the account, save and apply settings.
Step 3:
Wait a few moments (or if rebooting please wait until the phone has fully rebooted, connected to the network and attempted to register).
Step 4:
Stop the packet capture and download it to your computer. You will need a packet capture software such as Wireshark to view this file which can be downloaded here.
Step 5:
Filter the packets to only contain SIP using sip.CSeq contains "REGISTER":
As we can see in the packet capture the IP Phone (Source address: 192.168.2.100) is sending a Request to Register with the UCM62xx at IP Address 192.168.2.1.
The UCM62xx is then returning a 401 Unauthorized message back to the IP Phone (192.168.2.100).
Multiple 401 Unauthorized requests indicate that the SIP registration password is invalid.