cdp and log entries from unconnected devices

Discussion in 'Cisco' started by Bill F, Jan 11, 2005.

  1. Bill F

    Bill F Guest

    We have a 2912 in a colo connected to a "managed" non-cisco switch, an
    olicom, I believe. I'm seeing this error get logged. It seems to imply
    that fa0/1 on our switch is connected to 2651a.datatelmail.net. But,
    that isn't the case, so, what does this message mean? And, why are these
    unconnected devices showing up in a cdp discovery? Is it because the
    connected switch isn't blocking the cdp multicast?

    ..Jan 10 01:05:28: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
    FastEthernet0/1 (not half duplex), with 2651a.datatelmail.net
    FastEthernet0/1 (half duplex).

    here's the cdp neigh det output on our 2912
    -------------------------
    Device ID: switch8.*
    Entry address(es):
    IP address: *.*.*.*
    Platform: cisco WS-C3548-XL, Capabilities: Trans-Bridge Switch
    Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/2
    Holdtime : 130 sec

    Version :
    Cisco Internetwork Operating System Software
    IOS (tm) C3500XL Software (C3500XL-C3H2S-M), Version 12.0(5)XU, RELEASE
    SOFTWARE (fc1)
    Copyright (c) 1986-2000 by cisco Systems, Inc.
    Compiled Mon 03-Apr-00 17:31 by swati

    advertisement version: 2
    Protocol Hello: OUI=0x00000C, Protocol ID=0x0112; payload len=27,
    value=00000000FFFFFFFF010121FF0000000000000002B963CE00FF0001
    VTP Management Domain: 'hurricane2'

    -------------------------
    Device ID: 2651a.*.*
    Entry address(es):
    IP address: 65.19.189.6
    Platform: Cisco 2651XM, Capabilities: Router Switch IGMP
    Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/1
    Holdtime : 166 sec

    Version :
    Cisco IOS Software, C2600 Software (C2600-IPVOICE-M), Version 12.3(7)T,
    RELEASE
    SOFTWARE (fc1)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2004 by Cisco Systems, Inc.
    Compiled Sat 21-Feb-04 14:41 by eaarmas

    advertisement version: 2
    VTP Management Domain: ''
    Duplex: half

    -------------------------
    Device ID: 2651a.*.*
    Entry address(es):
    IP address: 10.10.10.1
    Platform: Cisco 2651XM, Capabilities: Router Switch IGMP
    Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/0
    Holdtime : 162 sec

    Version :
    Cisco IOS Software, C2600 Software (C2600-IPVOICE-M), Version 12.3(7)T,
    RELEASE
    SOFTWARE (fc1)
    Technical Support: http://www.cisco.com/techsupport
    Copyright (c) 1986-2004 by Cisco Systems, Inc.
    Compiled Sat 21-Feb-04 14:41 by eaarmas

    advertisement version: 2
    VTP Management Domain: ''
    Duplex: half
     
    Bill F, Jan 11, 2005
    #1
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  2. Bill F

    Hansang Bae Guest

    On Tue, 11 Jan 2005 00:19:58 GMT, Bill F <>
    wrote:

    >We have a 2912 in a colo connected to a "managed" non-cisco switch, an
    >olicom, I believe. I'm seeing this error get logged. It seems to imply
    >that fa0/1 on our switch is connected to 2651a.datatelmail.net. But,
    >that isn't the case, so, what does this message mean? And, why are these
    >unconnected devices showing up in a cdp discovery? Is it because the
    >connected switch isn't blocking the cdp multicast?


    [snip]

    Correct. Devices that do no understand cdp simply forward it on
    because it's a multicast frame. So your Olicom device is forwarding
    on the information from the far side.

    You can a) turn off CDP on that port or b) trying using CDP version 1
    which _I believe_ does not check for duplex mismatches or native VLAN
    mismatches.



    hsb


    "Somehow I imagined this experience would be more rewarding" Calvin
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    Hansang Bae, Jan 11, 2005
    #2
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