Problem with cisco VLAN - 2960 switch

Discussion in 'Cisco' started by Tom, Sep 4, 2012.

  1. Tom

    Tom Guest

    Hello,

    We have a small network (/28 mask) with two PC's and manually configured IP's.

    PC's are connected to the 2960 switch on two VLAN ports to allow only two PC's at a time on this VLAN. This switch is trunked to a 1800 series router.

    The problem is, if we remove a PC and try to connect another different PC with the same IP, the PC will not work unless the switch is reset.

    Question - Is there a way to automate this so the switch does not have to be touched each time a new PC is connected?

    Thanks.
     
    Tom, Sep 4, 2012
    #1
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  2. Tom <> writes:
    >We have a small network (/28 mask) with two PC's and manually configured IP's.


    >PC's are connected to the 2960 switch on two VLAN ports to allow only two PC's at a time on this VLAN. This switch is trunked to a 1800 series router.


    Interesting odd setup.

    >The problem is, if we remove a PC and try to connect another different PC with the same IP, the PC will not work unless the switch is reset.


    >Question - Is there a way to automate this so the switch does not have to be touched each time a new PC is connected?


    Most likely you have an ARP cache issue. In your little setup,
    resetting the ARP cache timer downwards to a minute or so shouldn't
    cause any issue, and then you may just have to wait a minute after you
    change the IP address on a machine.

    Or login to the switch and "clear arp".
     
    Doug McIntyre, Sep 4, 2012
    #2
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  3. Tom

    Tom Guest

    On Tuesday, September 4, 2012 8:48:33 AM UTC-4, Doug McIntyre wrote:
    > Tom writes:
    >
    > >We have a small network (/28 mask) with two PC's and manually configured IP's.

    >
    >
    >
    > >PC's are connected to the 2960 switch on two VLAN ports to allow only two PC's at a time on this VLAN. This switch is trunked to a 1800 series router.

    >
    >
    >
    > Interesting odd setup.
    >
    >
    >
    > >The problem is, if we remove a PC and try to connect another different PC with the same IP, the PC will not work unless the switch is reset.

    >
    >
    >
    > >Question - Is there a way to automate this so the switch does not have to be touched each time a new PC is connected?

    >
    >
    >
    > Most likely you have an ARP cache issue. In your little setup,
    >
    > resetting the ARP cache timer downwards to a minute or so shouldn't
    >
    > cause any issue, and then you may just have to wait a minute after you
    >
    > change the IP address on a machine.
    >
    >
    >
    > Or login to the switch and "clear arp".


    Thanks for the quick response Doug.

    Yes...this is a unique network aboard a ship at sea and resources are limited because of satellite communications.

    I actually was just about to set the arp timeout and saw your response. Give me more confidence now:)

    Seems this can be set on the router and the switch for this VLAN. I set both for now.

    Thanks again!
     
    Tom, Sep 4, 2012
    #3
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