#Yealink t21p e2 firmware update upgrade#

So I do want to take a moment and give them kudos but also like their knowledge base article. I never would have found that out if it wasn't for So I want to say 90% if not 95% of all the issues I've experienced over these years has been attributed to a bad design flaw and 1 setting. It should be a stupid device at that point. It shouldn't even be able to affect anything. The Arris modem forcibly still encapsulated the SIP ALG which was the whole problem.

Rebooted the modem, router, switches, my AD controller, everything. So went back in and disabled it again, of course all the phones couldn't register, with no reason as to why. We also had SIP ALG enabled on the UBNT router, however previously we disabled this like last year and it caused havoc, never understood why considering that is a recommended step.

#Yealink t21p e2 firmware update upgrade#

So my troubleshooting steps were to obviously check the phone settings, upgrade the firmware, reset to default settings and reconfigure each one individually. So the modem when bridged, still had a SIP ALG setting which caused all the havoc. Apparently even when bridged, the modem still has a way to affect networking and it's possible it's be intention or bad design flaw or just plain ole ignorance.

So the modem is an Arris DG model which is a combo modem & router with Wi-Fi. I can't take kudos for anything other than doing the right thing and checking each part of the network stack but also feeling inadequately prepared for the situation.