voip packet fight

VOIP Packet Fight
By Tony Fortunato, Sr Network Performance Specialist, The Technology Firm – www.thetechfirm.com
Working on an issue with a client where his VOIP phone’s get stuck at the ‘initialization’ process. As we chatted over the phone we quickly determined that this issue occurs when a phone is powered off and back on. The client also mentioned that this seemed to start about a year ago when they got a new router installed.
I asked how he typically resolved the issue and he said “I just reboot stuff until everything works”. I have to give him credit, at least he was honest.
Just a few things I checked when I got on site:
- Yup, the problem is definitely repeatable which is a huge plus when troubleshooting.
- Verified that the phone had a link light on its Ethernet port
- Phone reports that it has an ip address assigned that we can ping
- Tested the PC pass through port with my laptop which works fine
Now I’m intrigued and need a trace file to see what’s going on. Like all POE devices the challenge is how I capture the packets as the phone boots up. Oh yeah, and the switch is managed by a third party so we don’t have the option to set up a monitor/span port. Other options would be to use an external power supply for the phone and a tap or even an old 10/100 true hub.
That’s when I reached into my bag and reached for my Profitap/ProfiShark tap (https://www.profitap.com/profishark-1g/) since I can connect the tap inline between the phone and the switch port. I run into many switch configurations that have some sort of port security, so I want to avoid locking out a port. The ProfiShark connects to my computer via an USB3 port, keeping my MAC address out of the switch port and trace file as well as passing POE through ....

full article at
https://www.networkcomputing.com/networking/voip-packet-fight-troubleshooting-phone-initialization-problems