Catalyst 4000: Device connected to switch but no MAC address?!

Discussion in 'Cisco' started by Chris, May 24, 2006.

  1. Chris

    Chris Guest

    I inherited a pair of Catalyst 4000s with about 100 devices connected
    to each. I'm slowly going through and naming all of the ports (by a
    combination of 'show cam dynamic' and a list of MAC & IP addresses I
    have for our system), and came across one rather strange thing.

    sh port 4 | I 4/15
    4/15 unknown-weird connected 1 normal a-full a-1Gb
    10/100/1000
    4/15 none none
    4/15 disabled shutdown 0 0 1 disabled
    122
    4/15 0 - - - -
    -
    4/15 Enabled
    4/15 on on desired on 0 0 0

    4/15 connected auto silent 292 0
    4/15 connected - Enable No
    Change
    4/15 - 0 0 0 0
    4/15 0 0 0 0 0 0
    0

    So, something's connected to it at 1Gbit and has negotiated full
    duplex. But check this out:

    sh cam dynamic 4/15
    * = Static Entry. + = Permanent Entry. # = System Entry. R = Router
    Entry.
    X = Port Security Entry $ = Dot1x Security Entry

    VLAN Dest MAC/Route Des [CoS] Destination Ports or VCs / [Protocol
    Type]
    ---- ------------------ -----
    -------------------------------------------
    Total Matching CAM Entries Displayed =0

    It's the only device (out of the 200 or so) that does NOT have a MAC
    address. How is that even possible? I can't pull out the cable and
    unplug the device in question, at least not yet..!


    Chris
     
    Chris, May 24, 2006
    #1
    1. Advertisements

  2. Chris

    Mike Delaney Guest

    All that means is that the device in question hasn't transmitted anything
    recently. Dynamic CAM entries age out of the table, just like learned ARP
    entries do. Use 'show cam agingtime' to see what the timeout is currently set
    to. IIRC, the default is 300 seconds.
     
    Mike Delaney, May 24, 2006
    #2
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.