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My company has alot of outside suppliers and contractors who need access to our wifi network. Currently, we only allow DHCP to hand out 20 addresses for our quest Wifi network. This typically fill up very quickly due to cell phones, laptops, etc. Is there any way to 'lock' a specific IP/DHCP mapping to a specific computer/device, such that ONLY that device will be handed a specific IP from DHCP? This would ensure that they could always connect, instead of me manually having to clean all the junk out of the DHCP so they can get an IP address.

VLANing off and freeing address space is obviously the solution, but we have recently begun a full overhaul of the network infrastructure so we aren't quite ready for that. This a temporary solution for the time being just to keep outside consulatants happy and less complain-y.

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2 Answers 2

up vote 2 down vote accepted

Most DHCP servers have a thing called "reservations" which will cause the DHCP server to always hand out an assigned address to a requestor with a specific MAC address. Some can even create a reservation the first time a device asks for an IP. You need to look into the capabilities of your DHCP server (or router, if the DHCP server lives there.)

The DHCP protocol doesn't support the notion of users so this is probably the best you can do.

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Yup, this was exactly what I was looking for! –  Lee Harrison Sep 27 '12 at 18:05

I think you are looking for DHCP reservations. Here is an example of setting one on a Cisco router (toward the bottom of the page).

Named Mars The MAC address of the client is 02c7.f800.0422 and the IP address of the client is 172.16.2.254.

ip dhcp pool Mars
host 172.16.2.254
hardware-address 02c7.f800.0422 ieee802
client-name Mars

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