Cisco Linksys SPA Phone Date/Time Incorrect
The date or time on a Cisco Linksys SPA series IP phone is wrong even though an NTP server is configured. Fix it by adding the correct timezone and DST rules to the phone's TFTP config file.
Troubleshooting
Phantom (Ghost) Calls on VoIP Phones
Phantom or ghost calls are unsolicited ringing caused by automated SIP port scanners or bad actors targeting exposed IP phone ports.
Polycom Handset Falls Off Hook
The Polycom phone handset keeps slipping off the cradle. Switch the retaining tab position to secure it.
Polycom VVX Phone Asking to Sign In After Activation
After provisioning a Polycom VVX phone, the screen shows 'Line Unregistered' and a Sign In prompt. Fix it by changing the Base Profile to Generic.
Polycom Phone Shows 'SIP URI Disabled'
When a Polycom phone displays 'SIP URI Disabled', outbound calls fail and inbound calls go straight to voicemail. Fix it by restoring internet connectivity or requesting a firmware update.
Polycom VVX Phone Enters Letters Instead of Numbers When Dialing
When a Polycom VVX phone accepts letters instead of numbers during dialing, the dial mode has been set to URL mode. Switch it back to Number mode.
SIP/VoIP Registration Issues with Fortinet Firewalls
IP phones failing to register or dropping calls behind a FortiGate firewall. Covers SIP ALG, firewall policies, IPS, and NAT configuration.