cisco 7940G phone and Protocol Application Invalid

Discussion in 'Cisco' started by tg, Nov 18, 2008.

  1. tg

    tg Guest

    I'm an absolute beginner with a cisco 7940G phone:
    display says 'Protocol Application Invalid'.

    I bought this phone off ebay so I could learn about IP phones, (it
    arrived only this morning) but google shows this is also called a
    'bricked' phone.
    I don't know where to start with this problem. I have a cisco router and
    I'm familiar with that using hyperterminal but I don't know how to track
    down the ip address inside this phone, it has no console port. I'm also
    familar with tftp (I use tftfd32) but again I don't know how to find the
    ip address of the phone or some point to start at. I've trawled numerous
    cisco docs and other stuff on google but I'm stuck. I did a factory
    reset of the phone that proceeded correctly (powered up while holding
    the # key in) but then the Protocol Application Invalid message came
    back. None of the buttons on the phone produce any response. Thanks for
    any pointers.
    tg, Nov 18, 2008
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  2. tg

    Trendkill Guest

    First, here is a link to describe the problem, which is most likely a
    subnet/IP mismatch and inability to get to its image or boot file:

    What is your VoIP server going to be?

    If we are talking asterisk or trixbox, you will need to install a SIP
    image, get the necessary boot/config files on a tftp server, make sure
    you match the mac and username/passwords appropriately. The phone
    needs to boot, get an IP and tftp address (or you need to configure
    manually by unlocking the phone (pass should be cisco123 i think), and
    setting IP and tftp manually), and get to the config files that tell
    it what server to communicate with. The process is similar with CM or
    CM Express, although the config on the server is different.
    Trendkill, Nov 18, 2008
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  3. tg

    tg Guest

    First, here is a link to describe the problem, which is most likely a
    subnet/IP mismatch and inability to get to its image or boot file:

    thanks for your response but I'd already seen the above doc before
    posting. This doc is confusing because when it gets to the workaround
    section there's no such thing on my pc as Start > Programs >
    Administrative Tools > DHCP. I'm back where I started.

    And I know about having to install a SIP image, but I can't do any of
    that until I first clear this PAI problem.
    tg, Nov 18, 2008
  4. tg

    Trendkill Guest

    What subnet is this device plugging into? Does that device provide
    DHCP? Is the phone configured with a static IP? Does the static IP
    match the subnet that is configured on the switch? The advice in that
    article presumes you are running a windows server which is provided
    DHCP, I'm guessing you are using a router or something else. This
    sounds like a basic network mismatch to me.
    Trendkill, Nov 18, 2008
  5. tg

    tg Guest

    should I get this server pack?
    the DHCP server on my network is a cisco 2651XM router. PC's on the
    network pick up IP addresses given out by the router but I don't know
    how to ascertain if the phone is doing that, or if it has a fixed ip
    address inside it. Is there a default IP in the phone after a factory
    reset? The 'protocol application invalid' message seems to lock the
    phone out completely.
    tg, Nov 18, 2008
  6. tg

    tg Guest

    172.16.1.xx 2550 255.0.0
    yes it's a cisco router set as the DHCP server
    dunno, that's what I can't find out
    dunno, I haven't been able to ascertain the phone's IP, if it has one
    I agree, but I need to get some kind of start point established with the
    phone. This is the whole problem I'm having. I don't klnow what the IP
    address of the phone is. There must be a way to find out but I don't
    know what that is.
    tg, Nov 18, 2008
  7. tg

    tg Guest

    I had a breakthrough, I found the phone's ip address.
    so now I know that, I next need to clear up this
    'Protocol Application Invalid' thing.
    tg, Nov 18, 2008
  8. tg

    bod43 Guest

    This document:-

    States that the PAI error mesage can occur if the
    phone is doing DHCP and is not getting its
    expected "option 150" setting. This basically is
    the address of the "Call Manager".

    Here is what a Cisco router DHCP server looks like
    with option 150.

    ip dhcp pool home-net-low
    import all
    option 150 ip

    That was *working* with a cisco phone
    in a Call Manager confiuration (SCCP).

    Of course you do not seem to have a call manager
    so if this is the issue you may not get much further.

    In my experience if these these phones are unhappy
    they reboot, then get unhappy and reboot again....

    Unhappy means:-
    No call manager
    No dhcp
    No ethernet port

    Makes the live installations quite robust.
    Whatever you change the phone notices and reboots
    fixing itself.

    The call manager first provides a TFTP server
    where the phone looks for image updates
    and config info.

    Ah yes it's coming back to me.
    The 150 option I think is actually just the tftp server
    and it gets a config file from there which specifies the call
    manager's IP.
    In a default installation the tftp server is on the call manager.
    Hence my confusion.

    The phone can also be configured manually. Process is in the

    Hope this assists.
    bod43, Nov 19, 2008
  9. tg

    bod43 Guest

    You will need the SIP image for the phone too:-
    The default image will most likely only support SCCP.

    "Step 1 Go to the following URL:

    Step 2 To download the firmware for the Cisco Unified IP Phone
    7960G and 7940G (SIP), select the following file and follow the


    Note The following files are automatically installed when
    you run the P0S3-08-9-00.cop file: P0S3-08-9-00.loads,
    P003-08-9-00.sbn, P0S3-08-9-00.sb2, and P003-08-9-00.bin."

    This seems to require a login.
    bod43, Nov 19, 2008
  10. tg

    tg Guest

    thanks for your response.
    I managed to get further progress with the phone by plugging it into my
    router port and setting the port up with the following commands:
    ip dhcp pool test
    option 150 ip

    the Protocol Application Invalid message has no gone but it's replaced
    with 'TFTP timeout' and the phone is still bricked. Obviously the phone
    is trying to download via TFTP but I can't TFTP the phone at all. My
    TFTP server (pumpkin v2.7) just keeps failing. None of the buttons on
    the phone do anything, they appear to be dead. From what I can gather
    the phone's ip is, but how do I ascertain what address the
    phone is calling to for TFTP? I tried running wireshark to see the ip
    activity but nothing is coming from the phone.
    When I first turn the phone on I get 'Configuring VLAN', then I get
    'Requesting Configuration' and then I get 'TFTP timeout'.
    tg, Nov 19, 2008
  11. tg

    alexd Guest

    If it's trying to TFTP, then it's not bricked.
    Try a different TFTP server, perhaps?

    Although it's Asterisk-specific, you might be able to glean some information
    from this:
    alexd, Nov 19, 2008
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