Change Cisco 7912G IP Phone Firmware from SIP to Skinny

    In the process of writing a continuation to the first part of the topic on setting up telephony on Cisco, it was necessary to attach two phones to CME, but I ran into one problem. The phones were flashed under SIP, but at this stage I wanted to do everything on Skinny. And if there are no special problems with the Skinny-phone firmware in SIP (this process has already been described on Habré ), then the reverse procedure turned out to be very non-trivial.

    So, there are 2 ways to solve this problem, one of them is to use the full Cisco Unified Call Manager deployed on the server. Since his hands had not yet reached him, this option was unacceptable.
    The second solution is flashing with a CME router.
    First you need the firmware itself, the latest version on the Cisco website is now 8.0 (4), the file for downloading is called . But there is a problem, to download it, you need the privileges of the MTR account, which I do not have, so I had to look for an alternative source . The archive contains the file CP7912080003SCCP070409A.sbin.
    Next, upload the file via TFTP to the router and create the DHCP configuration for the phone:
    ip dhcp pool PHONES
    #опция 150 определяет адрес TFTP-сервера
    option 150 ip

    After that, run the necessary debug debug ip dhcp server events and debug tftp events debugs and see what happens.
    Jun 1 02:41:05.447: DHCPD: Sending notification of ASSIGNMENT:
    Jun 1 02:41:05.447: DHCPD: address mask
    Jun 1 02:41:05.447: DHCPD: htype 1 chaddr 0019.2f9c.554e
    Jun 1 02:41:05.447: DHCPD: lease time remaining (secs) = 86400
    Jun 1 02:41:05.527: TFTP: Looking for gk00192f9c554e
    Jun 1 02:41:05.539: TFTP: Looking for gkdefault.cfg

    It can be seen that the phone normally received DHCP address and correctly sends requests to the router, which acts as a TFTP server. The phone requests a configuration file either specifically for itself (gkxxxxxxxxxxxx, where xxxx is the phone’s mac address) or the default config. If you believe the official sources, CP7102 will ask for files starting with ff , and CP7105 with id.

    At this stage, our task is to slip the necessary configuration file into the phone so that it can be transferred to SCCP. You can read here what this file is and what fields it contains .

    So, create the gkdefault.txt configuration file


    Since you need to download it in binary form, you need to convert it with the cfgfmt.exe utility , which can be taken here . The utility also needs the sip_ptag.dat file for work , which lies in the same place.
    Run the program
    cfgfmt -tsip_ptag.dat gkdefault.txt gkdefault.cfg

    The resulting file is also uploaded to CME.

    So, after all the procedures, we should have the following on the flash:

    CME#sh flash:

    System flash directory:
    File Length Name/status
    1 18296372 c1700-ipvoicek9-mz.124-25.bin
    2 341023 CP7912080003SCCP070409A.sbin
    3 62 gkdefault.cfg

    Now add the necessary files to our tftp server:

    tftp-server flash:CP7912080003SCCP070409A.sbin
    tftp-server flash:gkdefault.cfg

    At this stage, you can distort the power of the phone and if everything is configured correctly, the following will be seen in the debugs:
    Jun 1 03:48:33.495: DHCPD: Sending notification of ASSIGNMENT:
    Jun 1 03:48:33.495: DHCPD: address mask
    Jun 1 03:48:33.495: DHCPD: htype 1 chaddr 0019.2f9c.554e
    Jun 1 03:48:33.495: DHCPD: lease time remaining (secs) = 86400
    Jun 1 03:48:33.575: TFTP: Looking for gk00192f9c554e
    Jun 1 03:48:33.587: TFTP: Looking for gkdefault.cfg
    Jun 1 03:48:33.587: TFTP: Opened flash:gkdefault.cfg, fd 0, size 62 for process 127
    Jun 1 03:48:33.595: TFTP: Finished flash:gkdefault.cfg, time 00:00:00 for process 127
    Jun 1 03:48:33.599: TFTP: Looking for CP7912080003SCCP070409A.sbin
    Jun 1 03:48:33.603: TFTP: Opened flash:CP7912080003SCCP070409A.sbin, fd 0, size 341023 for process 151
    Jun 1 03:48:40.279: TFTP: Finished flash:CP7912080003SCCP070409A.sbin, time 00:00:06 for process 151

    After that, Write flash ... Please wait will appear on the phone’s screen , it will reboot and become a Skinny-phone!

    As an alternative, it was possible to raise a DHCP server using tftpd32.exe , configure the 150th option in it and upload the files CP7912080003SCCP070409A.sbin and gkdefault.cfg to the root folder of the TFTP server.

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