I have a network configured in the following fashion:

                   |-> Imaging server (
                   |-> range
Internet->Router A-+-> Router B-⊺-> DHCP Server (Windows Server 2003,
                                |-> range

Is it possible to configure the DHCP Server to give out IP addresses to both ranges? Would it need to be directly on the Router A network?

A few more details: Routers A & B are both D-link routers with DHCP off. Router A (DI-624) connects via PPPOE to the internet, and has an internal IP address of Router B (DI-604) is statically assigned to connect to Router A, and has an internal IP address of

I've tried forwarding port 68 on Router A (DHCP requests), and made sure all other DHCP services are off (Router A, Router B, imaging server). Eventually, I'd also like to be able to set up the imaging server (Ubuntu/Fog Project) to serve all computers on the network via PXE boot.

I've seen this question, but I'm unsure how to configure my router as a DHCP helper (possible with a bare-bones D-link router?), as the only DHCP related options seem to be turning the service off and on.

As an aside, is it necessary for that last number of the IP address to be discrete across both ranges?

  • As an aside, is it necessary for that last number to be discrete across both ranges? I do not understand that question. – Wesley Apr 11 '12 at 18:51
  • @WesleyDavid I was having trouble wording that, my apologies for the ambiguity. I've seen examples where a first IP range will be from, and the second IP range from Since the 3rd number in the IP address is the same, I'd assume it doesn't matter whether or not I use the same range for the fourth number, i.e., the second IP range could be without conflicting. Does that help clarify what I'm asking? – Hannele Apr 11 '12 at 20:33
  • @WesleyDavid Ah, it was answered below. Thanks nevertheless! – Hannele Apr 11 '12 at 20:35
  • As long as the ranges are on separate subnets, it's all good. =) – Wesley Apr 11 '12 at 20:35

You'll need a little more equipment to make this work. Forwarding port 68 doesn't help because DHCP requests use broadcast packets - which won't get forwarded outside of the local subnet. If you want devices connected to Router B to get a DHCP address from Router A, you'll need a DHCP Relay Agent. Neither of the D-Link models you list does this, but they're on Windows Server since 2003 (http://technet.microsoft.com/en-us/library/cc781416%28v=ws.10%29.aspx) and Linux (http://linuxcommand.org/man_pages/dhcrelay8.html).

This will give you a system where devices behind Router B get addresses from the same pool as Router A. You could give devices behind Router B their own subnet if you run dhcpd on the Ubuntu server and configure it properly.

As for the last question, if you've got one subnet that's 192.168.1.XXX and one that's 192.168.2.XXX, there's no problem with their last octet overlapping. and are distinct, and won't interfere with each other.

Edit: Looking back at your question, if you're going to be PXE-booting devices on this network, you're definitely going to need the imaging server to be the DHCP host - Router A doesn't support the right DHCP options to make PXE happen.

| improve this answer | |
  • Interesting. Thanks for pointing out my next steps! – Hannele Apr 11 '12 at 20:45

Yes this can be done. However, it can't be done with the equipment you currently have. The crux of the problem is Router A. The DI-624 does not support DHCP relay / forwarding / helping (depending on what the equipment manufacturer feels like calling it).

You'll need to use a router that can pass DHCP across subnets. As Zoredache reminded me, you can have helper agents on devices other than routers. For Windows, look into the DHCP Helper Agent.

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  • 2
    The router doesn't have to pass the DHCP request. An agent can be installed on something in the other subnet. – Zoredache Apr 11 '12 at 19:49
  • @Zoredache Wow, I fail. facepalm Totally forgot about that. – Wesley Apr 11 '12 at 19:52

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