This is very strange problem. I have 5 sets of 335 phones at this locaton which has Verizon DSL. it has worked for 3 months. About 2 weeks ago it stopped registering. so what I did is:
1. bring these phones to another locaton which has Cable service, and they worked without any setting changes. I thought that it might be router problem so I switched routers between the 2 sites, but location that uses verizon dsl will not work. .
2. thinking the verizon might block sip. so I tried using softphone X-lite( also using sip) and it work.
I can't figure out why this happen. It just does not make any sense. Can someone give me help?
welcome to the Polycom Community.
Did you check with Verizon Support if they changed anything on their Network End as the Phone clearly works as you already verified.
I would assume that X-Lite [Edit by Mod] may not register to Port 5060 or something else but only a wireshark trace or a look at the logs would tell.
Please check the FAQ.
Polycom Global Services
I did use wireshark. at phone site I can see that polycom phone is generation some info. but at server site nothing.