I need to setup a lab network in our office that are on a different range of IPs. How do I distinguish the computers on the lab network from our corporate network so that the DHCP server knows to give these a different IP?

Our DHCP server is running Windows Server 2008

  • 5
    Why not put them on a vlan with their own DHCP server?
    – DanBig
    Mar 8, 2011 at 13:01
  • I don't have any other Windows licenses to create an additional DHCP server.
    – Luniz
    Mar 8, 2011 at 13:11
  • What type of switches/routers are there between the server and hosts? Mar 8, 2011 at 13:19
  • There is a Cisco Catalyst switch between the lab network and the DHCP server.
    – Luniz
    Mar 8, 2011 at 13:23

3 Answers 3


Assuming you are using different VLANs, you can use ip helper in Cisco switch to configure a DHCP relay. Then you can distinguish the relayed clients in the DHCP server (by using GIADDR) and give them different addresses. See: http://routergod.com/trinity/ and http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_25_sec/configuration/guide/swdhcp82.html#wp1096758 and RFC 3046

  • I believe this may be the answer I'm looking for. Going to give this a look and will let you know. Thanks!
    – Luniz
    Mar 8, 2011 at 15:15

You question asks other questions but essentially you just need to;

  • define a second scope that's appropriately routed where required,
  • then expose that scope onto either a separate vlan, segment (via a specific NIC) or fill it with specific reservations for the lab machines so that it's not used for anything else.

Oh and the MS DHCP service lets you have multiple scopes on a single service without the need for any additional licences.

  • Defining the 2nd scope is easy, I understand how to setup that piece. Can you please explain how to expose that scope onto a separate VLAN without exposing it corporate VLAN? Filling it with specific reservations wouldn't work as there are constantly new machines being added to the lab network.
    – Luniz
    Mar 8, 2011 at 13:29
  • well your DHCP server would have to have a physcial or virtual network adapter and IP on that second vlan - i.e. NIC2 or if you're doing .1q trunking then over the vlan-specific virtual NIC. If you don't really need a second VLAN simply create the second scope to only have as many entries as lab machines and define a reservation in that scope for each reservation - make sure to 'fill' the range completely though ok.
    – Chopper3
    Mar 8, 2011 at 13:54
  • This is a great answer and may very well have worked as well. However, the other answer is the one that I used and therefore was awarded the check. Thanks for your help in any case.
    – Luniz
    Mar 8, 2011 at 19:47

If you don't want to go the "create VLAN" route:

A workaround is to simply put all lab boxes behind another router/firewall with built-in NAT and DHCP, like a home gateway, etc. Now all lab boxes are segmented from production, still have Internet through production network, but can do their own broadcast traffic (i.e. DHCP) without bothering the production network.

  • Seems this would have worked had I chosen to go this route, thanks for your assistance.
    – Luniz
    Mar 8, 2011 at 19:48

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