Cisco 7940/7960 IP phones can support either the Skinny Call Control Protocol (SCCP) to run with Cisco CallManager, the Session Initiation Protocol (SIP), or the Media Gateway Control Protocol (MGCP), but not more than one simultaneously. This is possible because different firmware versions on bootup are loaded. This functionality is transparent to the end user, and you enable it through the changes to the basic text-based configuration files that the phones download from a Trivial File Transfer Protocol (TFTP) server.
If you use configuration files, the OS79XX.TXT file no longer controls the image used by the phone. The upgrade and image version are done through the image_version configuration parameter in the configuration files. Each SIP IP phone in the startup, attempts to download the configuration file SIPDefault.cnf. This file contains the image_version parameter that tells the phone which image to run. Thus, if you attempt to load the SIP version 7.1 software, SIPDefault.cnf must contain image_version: P0S3-07-1-00. If the image load differs from the one that is currently loaded on the phone, the phone contacts the TFTP server to convert to the new image.
In order to convert the SIP IP phone load that exists to MGCP, complete these steps:
Download the desired MGCP binary image from Cisco.com, MGCP IP Phone 7940/7960 and copy to the root directory of the TFTP server.
Open the SIPDefault.cnf file located in the root directory of the TFTP server with the use of an ASCII text editor such as Vi or WordPad. Find the configuration value image_version: and replace it with the MGCP firmware file name without the extension. For example P0M3-06-4-00.
Change the TFTP Server IP address in the IP Phone Network Configuration that points to the new TFTP server where the MGCP firmware is copied.
Note: In order to change the TFTP server IP address, you need to use the Unlock Configuration mode. In Release 4.2 and later, an Unlock Config item displays in the phone settings menu. When you select Unlock Config, you are prompted to enter a phone password with the use of the alphanumeric entry function of the keypad. The phone password is set to use the phone_password configuration parameter. When the correct password is entered, the configuration is unlocked and the settings can be changed.
When the Network Configuration or SIP Configuration menus display, the lock icon in the upper-right corner of the liquid crystal display (LCD) indicates an unlocked state. The unlocked symbol indicates that you can modify the network and SIP configuration settings. When the Settings menu is exited, the phone automatically relocks the configuration. In releases prior to Release 4.2 to unlock the Cisco SIP IP phone, press **#.
Reboot the IP Phone. During reboot, the phone sees the changed image_version: value and copies the MGCP image to the flash that reboots again with the new MGCP firmware with these states:
In order to verify check the version of the newly load image, choose Settings > Status > Firmware version. Look for the Application Load ID, which ideally is the same as the edited image name in the SIPDefault.cnf.