T20P Register Fail on Reboot

[amirscei]

Hi All! I'm new here and I would really appreciate if someone could help me with this.
We have at least 50 Yealink T20P IP Phones and some of them are acting very weird. Sometimes, when there's a power interruption, once the unit reboots, it won't be able to register on the phone server. I have to disable Account 1 and enable registration on Account 2 in order for the phone to work again. The main point is, every time the phones reboot, they can't register. Checked the Firmaware and it's updated. at least 10 out of 50 phones are acting like this. Need help urgently! thanks in advance!

[sergeysi]

I think it's better to check logs on PBX side, make SIP dump and analyze it.
Do your phones and PBX have NAT between them? If yes, there might be an issue with SIP ALG on the router.

[amirscei]

hi sergeysi. thanks for the prompt reply. i will try your suggestion later when i get to work, but i'm not sure what NAT has got to do with this issue. all the phones are connecting to 1 asterisk based pbx server and we've done that for a long time (even with Yealink SIP T18 before) and we've never encountered this problem. now for this phones, I can't even enable 2 lines because i am reserving the other line for this issue. on registration fail, all i do is disable the registration for the current line (account 1), then enable the other line (account 2) with the same sip account details and it's working. the same phone, same settings, but the first line registration always fails on reboot and have to manually set the other other line for registration.