So, you don’t have the trusty old butt set to do your troubleshooting for you with VOIP, so what’s a phone guy/gal to
do? First thing is some planning. When you put in a VOIP systems, it’s important that you build yourself some test points in the network, so you can insert, or extract data to do troubleshooting. Remember, its not as simple as pressing the bed of nails on the wire and listening anymore.
But, there are some other need tricks that you can do. For example. Ethernet switchs have a feature called Port Mirroring. Make sure the switches you install have Port Mirroring. Here is how it works. Lets say a phone you are having problems with sits on port 20 of your ethernet switch. And, lets say that you have your laptop on port 24. In the switch, you port mirror port 20 to port 24. Now, every packet to and from port 20 will also be sent to port 24, where you can see it on your laptop.
This is important, because on your laptop, you are going to install your newest best friend in networking – Wireshark. Wireshark is a packet capture program that grabs every packet on the line, and classifies them for you by protocol, IP address, port, you name it.
So, getting back to that telephone with issues. What you want to do it start wireshark and start capturing packets on the phone with issues. When wireshark opens, go to the Telephony tap on the menu, and scroll down to VOIP and click on that option. IT will open a new box that will allow you to follow the VOIP calls on the system. Now place a call to reproduce the issue you are trying to resolve.
Your call will appear in the Telephony/VOIP box, and you can select it and graph it, which shows the session and each step of the call setup and teardown, and you can also listen to the audio portion of the call as well, either incoming, outgoing, or both.
Clicking on a record in the graphic mode will open the actual packet from the trace to let you drill down further for details. This is a great opportunity to see exactly what your call is doing or not doing. Don’t forget, you can trace another port that doesn’t have the issue to see what a good call looks like as well, so you can do a stare and compare of the good call versus the bad call.
This is a great tool, that can save you a ton of lost hours troubleshooting on VOIP systems.
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