DHCP Snooping on Catalyst 3548XL Switches

Posted on 2012-08-14
Last Modified: 2012-08-15
I have manage the Ethernet network for an apartment building that consists of a 50Mb circuit, 7204VXR router, and five Catalyst 3548XL switches.  This building is full of users that love to connect wireless routers "backwards" into the LAN and backfeed DHCP into the network and screw everything up.  Is it possible to configure the 3548 switches to suppress this behavior?  If not, what is the cheapest switch model (on the refurb market) to gain this functionality.  Thanks!
Question by:David Blair
    LVL 3

    Expert Comment

    by:Dimitris Ioakimoglou
    run the "ip dhcp snooping" command on your switch and see if it accepts it.

    if it does you should also use "ip dhcp snooping vlan <number>" and "ip dhcp snooping trust"
    on trusted interfaces - except if you want to ban DHCP altogether.
    LVL 17

    Accepted Solution

    The 3500XL series is purely layer2, so you can't filter DHCP with that.
    The 2950 can do DHCP snooping, and it became out-of-support recently, so you can find good deals on ebay.

    LVL 1

    Author Closing Comment

    by:David Blair
    That's the info I needed.  Thanks!

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