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Cisco Phone Reads Offline - Cisco IP Phones

When your Cisco phone reads Offline, the first step is to power-cycle the network. Read more for the full steps to fix your Cisco phone when it reads Offline.


Your Cisco phone reads Offline. This sometimes happens suddenly after weeks or months of working properly.

Applies To

Cisco phones


  1. Power-cycle the network (this will usually resolve the issue for phones that had previously been working properly).
    • Modem
    • Router
    • Switch
    • Phone(s)
  2. Change Ethernet cable.
    • Use a different port or switch on the router.
  3. Try assigning a static IP address on the phone.
  4. Is the modem a combo device?*
    • Yes: Place in bridge or pass-through mode.
    • No: Continue to the next step.
  5. Check for and disable:*
    • SIP-ALG
    • SPI
    • Firewall
    • Restricted NAT

*If all Cisco phones in network are reading Offline.


The phone is unable to register with the SIP server.


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