cdp enable/disable?

Discussion in 'Cisco' started by Lisa Casey, May 18, 2007.

  1. Lisa Casey

    Lisa Casey Guest

    Hi,

    I have a Cisco 2610 (I think) router connected to a switch connected to my
    network. We recently received a couple of VOIP phones (Cisco IP-Phone 7940
    series). When I plug these into the network, my syslog receives the
    following error from the router once a minute:

    05-15-2007 16:39:39 Local7.Warning hope.jellico.com 387: 10w3d:
    %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not full
    duplex), with SEP001AE22A943D Port 1 (full duplex).

    I googled it and found some suggestions to just turn cdp off on the
    Ethernet0/0 interface of the router.

    This would get rid of the messages I'm receiving, but do I really want to
    do that? Are the messages I'm seeing real error messages indicating a
    problem I should resolve, or are they just informational, letting me know
    of something that is harmless?

    Thanks,

    Lisa Casey
    Lisa Casey, May 18, 2007
    #1
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  2. "Lisa Casey" <> writes:
    >I have a Cisco 2610 (I think) router connected to a switch connected to my
    >network. We recently received a couple of VOIP phones (Cisco IP-Phone 7940
    >series). When I plug these into the network, my syslog receives the
    >following error from the router once a minute:


    >05-15-2007 16:39:39 Local7.Warning hope.jellico.com 387: 10w3d:
    >%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not full
    >duplex), with SEP001AE22A943D Port 1 (full duplex).


    >I googled it and found some suggestions to just turn cdp off on the
    >Ethernet0/0 interface of the router.


    >This would get rid of the messages I'm receiving, but do I really want to
    >do that? Are the messages I'm seeing real error messages indicating a
    >problem I should resolve, or are they just informational, letting me know
    >of something that is harmless?



    No, you probably don't want to do that. You do have a duplex mismatch
    between the VOIP phone and the switch. The CDP messages are coming
    from the phone. The router is displaying them, even though its not the
    culpret (if the HP switch knew what CDP was, it'll stop them there).

    You probably have the phone force set to Full Duplex, which means that
    auto-negotiation is turned off, which the ethernet spec requires the
    side that is set to auto-negotiate (the switch) to fallback to half-duplex.
    Ie. standard duplex mismatch.

    Make sure the point where your phone is getting its network info is
    set to do auto-negoation rather than force duplex. Most likely its
    TFTP'ing its setup info from the callmanager, although its possible to
    manually setup the network info in them. Fixup the network settings
    there, and the messages should go away.
    Doug McIntyre, May 18, 2007
    #2
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  3. Lisa Casey

    Sam Wilson Guest

    In article <464db8bc$0$36725$>,
    Doug McIntyre <> wrote:

    > "Lisa Casey" <> writes:
    > >I have a Cisco 2610 (I think) router connected to a switch connected to my
    > >network. We recently received a couple of VOIP phones (Cisco IP-Phone 7940
    > >series). When I plug these into the network, my syslog receives the
    > >following error from the router once a minute:

    >
    > >05-15-2007 16:39:39 Local7.Warning hope.jellico.com 387: 10w3d:
    > >%CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not full
    > >duplex), with SEP001AE22A943D Port 1 (full duplex).

    >
    > >I googled it and found some suggestions to just turn cdp off on the
    > >Ethernet0/0 interface of the router.

    >
    > >This would get rid of the messages I'm receiving, but do I really want to
    > >do that? Are the messages I'm seeing real error messages indicating a
    > >problem I should resolve, or are they just informational, letting me know
    > >of something that is harmless?

    >
    >
    > No, you probably don't want to do that. You do have a duplex mismatch
    > between the VOIP phone and the switch. ...


    Probably not. I'd guess there's a non-Cisco switch between the phone
    and the router. The router sees a CDP neighbour reporting a full duplex
    connection (to the switch) but receives the messages on an interface
    which is running half duplex. It therefore complains. If there were a
    CDP-speaking switch between them those particular messages wouldn't get
    through.

    Sam
    Sam Wilson, May 18, 2007
    #3
  4. Lisa,

    Most likely you have your Cisco IP Phones connected to non-Cisco switch. CDP
    protocol usually doesn't cross Cisco switches - it works between two
    adjacent Cisco devices.

    You may be able to shut down these messages - go to the router, go to
    configuration mode, enter into the E0/0 interface, and issue the command "no
    cdp log mismatch". Something like:

    Router# config t

    Router(config)# int e0/0

    Router(config-if)# no cdp log mismatch

    I don't know what IOS version you are, however it should work.

    Good luck,

    Mike
    CCNP, CCDP, CCSP, Cisco Voice, MCSE W2K, MCSE+I, Security+, etc.
    CCIE R&S (in progress), CCIE Voice (in progress)
    ------
    PC Headset Adapters for Cisco IP Phones
    www.ciscoheadsetadapter.com
    www.headsetadapter.com


    "Lisa Casey" <> wrote in message
    news:...
    > Hi,
    >
    > I have a Cisco 2610 (I think) router connected to a switch connected to my
    > network. We recently received a couple of VOIP phones (Cisco IP-Phone 7940
    > series). When I plug these into the network, my syslog receives the
    > following error from the router once a minute:
    >
    > 05-15-2007 16:39:39 Local7.Warning hope.jellico.com 387: 10w3d:
    > %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on Ethernet0/0 (not
    > full duplex), with SEP001AE22A943D Port 1 (full duplex).
    >
    > I googled it and found some suggestions to just turn cdp off on the
    > Ethernet0/0 interface of the router.
    >
    > This would get rid of the messages I'm receiving, but do I really want to
    > do that? Are the messages I'm seeing real error messages indicating a
    > problem I should resolve, or are they just informational, letting me know
    > of something that is harmless?
    >
    > Thanks,
    >
    > Lisa Casey
    >
    >
    >
    >
    >
    >
    headsetadapter.com, May 18, 2007
    #4
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