How to convert a Cisco 7940 from SCCP to SIP

Note: This guide has been tested with firmware version pos3.08.2.00. Be aware that different firmware revisions may have different functionality.

This document will describe how to get a Cisco 7940 with SCCP (Skinny) protocol, convert it to SIP and get it to work with 3CX Phone System.

Step 1: Obtain the Firmware files

You will need the SIP image and the files necessary for the SIP upgrade. The following files should be provided by your CISCO phone supplier. These files are:

OS79XX.TXT – This file tells the phone which version of the firmware to load.
SipDefault.cnf – This file loads the default setting for every phone. Usually this includes where to register the phone.
SIP001A2F336152.cnf – This file has information specific to each phone. The 001A2F336152 (last 12 characters) of the file name is the phone’s MAC address, so you need to make sure this is correct for every phone you are upgrading.

The SIP image that we have used contains the following files:
OS79XX.TXT
P0S3-08-2-00.sb2
P0S3-08-2-00.sbn
P0S3-08-2-00.loads
P0S3-08-2-00.bin

Step 2: Prepare a TFTP Server to deploy the firmware files to the phone

Download any TFTP* server software. The one that was used in this specific SIP upgrade is called Pumpkin, but you can use any TFTP software.

Install the TFTP server. Make sure that you specify in the options the location on your TFTP server where the phone device should look for the SIP image files. Configure the TFTP server so that Read Request Behaviour is set to “Give all Files” without “prompt before giving file”. This way you make sure that the read request of the phone happens without any complications. (refer to figure 1)

Figure 1

* The Trivial File Transfer Protocol (TFTP) is normally used only for booting diskless workstations. The TFTP-server package provides the server for TFTP, which allows users to transfer files to and from a remote machine.

Step 3: Configure your DHCP Server to tell the phone where to get the Firmware files

Configure your DHCP server with the specific IP address of your TFTP server. If you are using the Windows 2003 DHCP server then the TFTP option is found on Scope Options/Configure Options/General Tab. Then tick/select option 066 which is the “Boot Server Host Name” and enter in the string value the IP address of your TFTP server. (refer to figure 2)

Figure 2

Step 4: Complete the upgrade

Put all the files along with the extracted SIP image files in the TFTP server root directory the one you defined on the TFTP server options and restart the device. The device will be assigned an IP/Gateway/DNS from the DHCP server as well as the TFTP server from which to load the SIP image and configuration files from.

Once restarted the phone loads the SIP image and the display will look very similar to the one in figure 3. Small differences include:

• below the Cisco logo it will say “Cisco systems Inc © 2000-2006”
• next to the number of the extension on the top right corner it will say extension SIP (for example 245SIP)
• and finally there is no Home soft button on the right on the display.

For details on how to build the configuration file of the CISCO 7940G phone please have a look at this FAQ.

** Please be aware that most CISCO phones do not support a web interface when the SIP image is loaded. The only way to configure is through a configuration file that will be loaded on the TFTP server or a telnet session.