I have a problem with my UC540, below is my network diagram:
I have successfully configured UC540, incoming and outgoing call working perfect, but when I changed IP address on UC540's F0/0 which connected directly to 887VA then incoming call stop working??? outgoing call still work fine.
Example: I change F0/0 on UC540 from 18.104.22.168/24 to 192.168.1.254/24 then incoming call dead, if I change F0/0 ip back to 192.168.1.200/24 then incoming call work normal
Note: After int F0/0 has a new ip address, I have to restart the unit or it took long time for incoming call to work as normal.
Even when ADSL2+ connection down for a few seconds only, incoming call still dead (will work again after Registrar time expired)
I also noticed that after IP address changed, UC540 keep sent invite but doesn't received unless Registrar expired.
Forgot to mention that I'm using SIP Trunk. Configure file attached with incoming call setting only for easy to troubleshooting.