Router as DHCP server and using ip helper at the same time?

My educated guess on this matter is that this will not be possible. My first thought was some kind of policy routing to pick out the one device on the subnet that needs special treatment and maybe do something sneaky like send it into a loopback interface which has perhaps an "ip helper-address" configured and hope that the helper address command overrides the DHCP server running on the same system.

However, note that the one device that needs this special treatment does not even have an IP address yet! So, policy routing is out. The only way to identify that device would be its layer 2 address and I can't see how with that constraint we could do this mix of DHCP server and DHCP relay functionality on the same box.

Cisco da Gama

What are the requesting devices attached to - a switch ? If so are the swiutch and the router capable of trunking ?

Please explain the requirement to have the boot request for one device to go to a different server

Yes, they are attached to a switch that is capable of trunking to the router. One device needs to get its address from a DHCP server that will then load an OS to it. All other devices get there address from the router no problem.

so you could put the switch port for that device on a separate vlan and enable trunking between switch ant the router.

Then on one vlan the router can be the local DHCP server, while the speical device is helpered to the desired server

The problem originally stated that a solitary device on a subnet needed this special treatment with a different DHCP server while other devices on that same subnet should use the IOS DHCP server. Moving the device to a separate vlan would mean moving it out of that subnet and putting it in a subnet of its own. It does seem reasonable to do something like that for this special case and so if you can afford to have two subnets instead of the one initially specified, the above suggestion should work and is very nice.

I was earlier assuming that for some reason you need to keep all those devices on the same subnet.

Cisco da Gama

Another thing I would investigate is if the server can be configured to unicast instead of broadcast its bootp request. AN IP helper would not be required in the case.

So put this one device in a new vlan by itself, same IP address but trunk the old and new vlan on the same router port?

Using a new vlan will mean a new IP subnet for the device using bootp.

BTW what is the device in question (make,model, OS version)