Causes

  • The Default Gateway IP Address on the DHCP Server was set to the wrong IP.
  • An Advanced DHCP Server Option is enabled but not configured or misconfigured.
  • The phone was manually configured with a static IP address but it was configured incorrectly.
    Note: manually configuring a phone with a static IP address is not supported.

Resolution

  1. Log in to the affected Polycom phone(s)
  2. Go to Diagnostics > View & Download Logs > Log File Type: App and scroll to the very bottom of the log
  3. Slowly scroll up until you see Gateway IP Address
  4. Verify the Gateway IP Address is the IP address of the main router on the subnet that the phones are using.
    • If the Gateway IP is correct, then proceed to step 5.
    • If it is not, you or your IT will need to login to the DHCP Server that is on your phone's network and correct the Gateway IP Address field. Reboot the phones once you complete this change.

      Important: if you do not have a DHCP Server enabled on the phone's network, you are required to enable one since we do not support manually configuring the phones with a static IP address. Instead, you can setup DHCP IP Reservations if you need the phones to always use the same IP address.

  5. If you did not resolve the issue in step 4, you or your IT will need to log in to the DHCP Server that is on your phone's network and check that each advanced DHCP Server Option is correctly configured. 
    • DHCP Option 44 (Vendor-Specific Information) & 43 (NetBIOS Over TCP/IP Name Server) are the most commonly enabled options that are mistakenly enabled or misconfigured, causing the Unknown Network Error message.