Configuring Linksys SPA-921 for 3CX Phone System

IMPORTANT This guide has been tested with firmware version 5.1.8. Be aware that different firmware revisions may have different web interface formats and functionality.
This FAQ is based on a new phone OR one that has been reset to factory defaults.

  1. Ensure that you have created the extension that you wish to use with the phone in 3CX Phone System first. Take note of the ID field and the password that you have entered for the extension.
  2. Connect the LINKSYS SPA-929 phone to the network and main power supply. The phone will boot up, and providing you have DHCP installed on your network, will obtain an IP and display it at the bottom of the phone’s LCD screen.
  3. Now point your browser to the web interface of the phone: ‘http://<phone-ip-address>’ where <phone-ip-address>is the IP address shown on the phone. (Refer to figure 1)
  4. Enter the password of the phone and click login to access the phone’s configuration. For this particular phone, the default password is admin


    Figure 1

  5. Click on ‘admin login’ on the upper right corner to enter the administration mode so you can configure the phone. (Refer to figure 2)


    Figure 2

  6. Now click on “advanced” on the upper right corner and proceed to the “ext1” tab to configure the first extension. Now configure the account for the phone. First of all make sure that ‘Line Enable’ under General is set to YES. (Refer to figure 3)
  7. In the Proxy and Registration category, enter the IP or FQDN of the 3CX Phone System server. If entering an FQDN, review this FAQ.
  8. Repeat the same setting for the Outbound Proxy option.
  9. In the Subscriber Information category, in the “Display Name” field enter the name you want to be displayed on the Phone display.
  10. Now proceed by entering in the “User ID” field which is the extension you want to associate with this phone.
  11. Enter a password for the user ID in the “Password” field.
  12. If you are planning to use an authentication ID, select YES in the ‘Use Auth ID’ field and enter the authentication ID in the “Auth ID” field.
    These fields must match the ID & password configured in the ‘ID’ & ‘Password’ fields in the Authentication section of the ‘Add Extension’ page in the 3CX Management Console.
  13. In the "Dial Plan" section, replace the contents of the "Dial Plan" field with "[x*]." (without the quotes).
  14. Now “submit all changes” which is on the bottom of your screen. Your phone will restart. After a few seconds your phone will register with the 3CX phone system. You can verify that on the Phone System\Line Status page of the 3CX management console.


    Figure 3

  15. Click on the ‘Phone’ tab to configure the Voice mail information
  16. Now proceed by entering ‘999’ in the “Voice Mail number” field.
  17. Click on the 'SIP' tab so as to configure the RTP packet size.
  18. Change the value of the 'RTP Packet Size' field to read '0.020.

Advanced features

To use some of the advanced features available in 3CX Phone System, your phone will require additional configuration. Note that these features will only work with the commercial editions of 3CX Phone System.

Configuring MWI (Message Waiting Indicator):

3CX can show that the user has new voice mails waiting via the MWI light. To enable this, go to the Extension 1 property page and  enable MWI by choosing the "yes" option from the drop down menu.
Linksys supports MWI only for the 1st extension configured on the phoneset.

SIP Phone Configuration Guides