Cisco 1221 AP to IP phone phone power issue

Discussion in 'Cisco' started by Emlynfluff, Feb 14, 2007.

  1. Emlynfluff

    Emlynfluff Guest

    I am are working on a solution for a county fire service. They
    recently have had a sizeable Cisco IP phone rollout, over their ~30
    stations.

    The next stage is to install phones in their Breathing Apparratus
    rooms, which we can't hardwire cat-5 in to. So, we're testing a
    solution, using Cisco 1231G AP's, the remote in workgroup bridge mode,
    to link via a wireless bridge, back to the LAN. We then plug a Cisco
    IP phone eg: 7912G, in via cross-over to the remote AP.

    The problem is when I plug a phone in to the Ethernet of the remote AP
    via cross-over cable, the phone switches off. This works fine
    conecting up my laptop.
    If I install a switch between the two devices, plug AP and phone in to
    that - it works. Because of the environement in the fire stations,
    we don't want to install a switch, we would like to use the cross-over
    direct in to the phone. (if possible!)
    I am assuming there is some kind of Cisco proprietary Inline power
    issue going on here, and the phone switches itself off, expecting to
    be powered via Inline?

    Customer doesn't want to use a wireless Cisco 7920 - they'd like a
    desktop phone, so we're stuck with a wireless workgroup bridge. We
    could use another AP, without Cisco Inline, but the 1200 is rugged,
    and deisgned for that envirnment, much preferred choice.

    How can we get the phone working with the access point, without the
    use of a switch?

    Any help here would be greatfully appreciated.

    Stuart.
     
    Emlynfluff, Feb 14, 2007
    #1
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  2. Hi Stuart,

    The AP1200 does not *supply* Power over Ethernet (although it can
    *consume* PoE. So if you're trying to power your 7912G from the
    AP, this can't work.

    So you would need to power your phone from a brick plugged into an
    AC power source (or some other how supply the phone with the 48VDC
    that it requires.)

    Regards,

    Aaron

    ---


    ~ I am are working on a solution for a county fire service. They
    ~ recently have had a sizeable Cisco IP phone rollout, over their ~30
    ~ stations.
    ~
    ~ The next stage is to install phones in their Breathing Apparratus
    ~ rooms, which we can't hardwire cat-5 in to. So, we're testing a
    ~ solution, using Cisco 1231G AP's, the remote in workgroup bridge mode,
    ~ to link via a wireless bridge, back to the LAN. We then plug a Cisco
    ~ IP phone eg: 7912G, in via cross-over to the remote AP.
    ~
    ~ The problem is when I plug a phone in to the Ethernet of the remote AP
    ~ via cross-over cable, the phone switches off. This works fine
    ~ conecting up my laptop.
    ~ If I install a switch between the two devices, plug AP and phone in to
    ~ that - it works. Because of the environement in the fire stations,
    ~ we don't want to install a switch, we would like to use the cross-over
    ~ direct in to the phone. (if possible!)
    ~ I am assuming there is some kind of Cisco proprietary Inline power
    ~ issue going on here, and the phone switches itself off, expecting to
    ~ be powered via Inline?
    ~
    ~ Customer doesn't want to use a wireless Cisco 7920 - they'd like a
    ~ desktop phone, so we're stuck with a wireless workgroup bridge. We
    ~ could use another AP, without Cisco Inline, but the 1200 is rugged,
    ~ and deisgned for that envirnment, much preferred choice.
    ~
    ~ How can we get the phone working with the access point, without the
    ~ use of a switch?
    ~
    ~ Any help here would be greatfully appreciated.
    ~
    ~ Stuart.
     
    Aaron Leonard, Feb 14, 2007
    #2
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  3. Emlynfluff

    Emlynfluff Guest

    Hi Araon, cheers for the reply.

    Yep, I understand the devices are clients receiving Inline power.

    The access point has its power supplied by the PSU.
    The phone is also using an external power adapter (cube) to supply its
    power. I connect external the power to the phone, it boots up, then
    connect the cross-over cable in to the phone-AP, the phone switches
    itself off.
    I believe the phone is doing some sort of Inline power negotiation,
    and since the AP also supports this (as a client), maybe they're
    getting confused? The phone could think that the AP can supply
    Inline power, so the phone swiches off external PSU, and chooses ILP
    as a preferred souce?
    I can't force the phone to use external power only, ignoring ILP. I
    can't disable Inline power on the AP..

    Any ideas how to work round this?
    I know sticking a switch in between the two devices works. I snipped
    the spare pins in the Ethernet cross-over cable, 4,5,7 & 8, but then
    read Inline power uses the same as Ethernet - damn it! ;) The
    spare cat-5 pins are used for the IEEE standard 802.3af, not Cisco
    proprietary ILP.

    Stuart.
     
    Emlynfluff, Feb 15, 2007
    #3
  4. ~ > Hi Stuart,
    ~ >
    ~ > The AP1200 does not *supply* Power over Ethernet (although it can
    ~ > *consume* PoE. So if you're trying to power your 7912G from the
    ~ > AP, this can't work.
    ~ >
    ~ > So you would need to power your phone from a brick plugged into an
    ~ > AC power source (or some other how supply the phone with the 48VDC
    ~ > that it requires.)
    ~ >
    ~ > Regards,
    ~ >
    ~ > Aaron
    ~
    ~ Hi Araon, cheers for the reply.
    ~
    ~ Yep, I understand the devices are clients receiving Inline power.

    ~ The access point has its power supplied by the PSU.
    ~ The phone is also using an external power adapter (cube) to supply its
    ~ power. I connect external the power to the phone, it boots up, then
    ~ connect the cross-over cable in to the phone-AP, the phone switches
    ~ itself off.

    Ah, ok, that was the OTHER possible interpretation of your setup
    that I entertained from your previous posting. I chose to assume
    the one that had the easier explanation :)

    So, given this report, my guess is that the phone is being confused
    by the CDP from the AP. So I would turn off CDP on the FastEthernet0:

    int faste0
    no cdp enable

    Does this help?

    Aaron

    ---


    ~ I believe the phone is doing some sort of Inline power negotiation,
    ~ and since the AP also supports this (as a client), maybe they're
    ~ getting confused? The phone could think that the AP can supply
    ~ Inline power, so the phone swiches off external PSU, and chooses ILP
    ~ as a preferred souce?
    ~ I can't force the phone to use external power only, ignoring ILP. I
    ~ can't disable Inline power on the AP..
    ~
    ~ Any ideas how to work round this?
    ~ I know sticking a switch in between the two devices works. I snipped
    ~ the spare pins in the Ethernet cross-over cable, 4,5,7 & 8, but then
    ~ read Inline power uses the same as Ethernet - damn it! ;) The
    ~ spare cat-5 pins are used for the IEEE standard 802.3af, not Cisco
    ~ proprietary ILP.
    ~
    ~ Stuart.
     
    Aaron Leonard, Feb 15, 2007
    #4
  5. Emlynfluff

    Emlynfluff Guest

    No joy there, I'm afraid.
    I've done a "no cdp run" on the AP, phone still switches itself off
    when I plug in the cross-over, and the phone is powered via PSU.

    I read that CDP is used after the device has recieved power, so it can
    suss out the devices actual power requirements, rather than wasting
    some of its limited power budget on a single device.

    Thanks for trying, I guess we may have to put a swtch between the 2
    devices, which is a shame.
     
    Emlynfluff, Feb 19, 2007
    #5
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