[asterisk-users] Digium IP Phones UNREACHABLE after registration

[Hermann Wecke]

I'm trying to solve a mystery for the last couple of days.

I have a mix of D70, D50 and D40 behind NAT. Server is in a
colocation, not a VPS.

For several years, everything was working fine, no issues. A few days
ago I started having problems at one particular site. NO CHANGES have
been made to this office network - same router, switch and internet
provider. No new equipment added or configuration changed (I only
upgraded the firmware and asterisk trying to solve the problem).

A few seconds after registration, the Digium phones will become
UNREACHABLE. Right after that, the entire VoIP network (where the
Digiums are located) will be also dropped - all other devices
(non-Digium) connected will be kicked from the asterisk box. There are
ObiHai, Yealink and Linksys at this location - all will be kicked.

The server remains operational and all other users/peers (not running
Digium phones) are up and running.

Sip debug and tcpdump didn't show any relevant information to solve
the puzzle. I also replaced the router (twice, different models and
firmware versions), PoE switch and cable modem. No success. IP is
dynamic but the provider will only change it once a year. Qualify=yes
(or no) didn't fix. Removing the password (deny/permit IP) also
didn't.

Running Asterisk 13.20.0, firmware 2.6.2.

Any ideas where I should dig further?