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How do I find a rogue DHCP server on a Cisco switch?

Posted on 2008-11-03
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I am having an issue with someone attaching a rogue DHCP server to my network.  I need to find out who is doing this, and so far I have come up with nothing.  I am assuming that I can somehow look at the switch activity when the rogue DHCP server is active to determine which port the traffic is coming from and shut it down, but I not sure what command to use or what to look at to see where the DHCP acks are coming from.
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Question by:warewols
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Don Johnston earned 500 total points
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You could stop from happening in the first place.
http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.1/13ew/configuration/guide/dhcp.html

Once it occurs, you would need to determine the MAC of the DHCP server from the workstation.
"arp -a"

The view the mac address table on the switch.
"show mac-address-table"

That will show you which port the rogue DHCP server is connected to.

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