Category Archives: SIP ALG

Disable SIP ALG on ZyXEL P661

Disabling SIP ALG – ZyXEL P661

 WARNING, deviating from these steps may cause the device to become non-responsive.

  1. Ensure the computer is connected to the router.
  2. From the Windows desktop open a Command Prompt window.
    Navigate: Start > All Programs > Accessories > Command Prompt.
  3. At the prompt type ipconfig then press the Enter key.
  4. From the Ethernet adapter Local Area Connection section, locate the Default Gateway address (e.g.,
    The Default Gateway address will vary depending upon the configuration.
  5. At the prompt type telnet then press the Enter key.
    If telnet is not recognized, you may need to use something like Putty (
  6. Enter the router password then press the Enter key.
    The default password is 1234.
  7. At the prompt type ‘ip nat service sip active 0′ without quotes, the last letter is a zero then press the Enter key.
  8. After being told that sip alg has been disabled, type in Exit.