RRAS and DHCP Relay lab setup / problems

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Hi all,

I have been struggling to get something working the last couple of days. I wanted to test out how I would go about setting up a DHCP Relay on a subnet instead of using a DHCP server or a router that would pass on the DHCP Traffic. So I have set a few machines up at work in order to try and simulate this scenario.

In subnet A we have a Domain Controller on IP 192.168.0.1/24. This is also a DNS server and a DHCP server with a scope set to give out addresses in the range 192.168.0.50 to 0.100.

For the sake of argument, also assume there are workstations in this subnet joined to the domain. There aren't but there could be ...

I have a PC that I have setup as a router. This server (server 2k3 installed) has 2 NIC's in it. One of which is set to 192.168.0.2/24 and is plugged into the same switch as the DC in Subnet A. The other NIC is set to 192.168.1.2/24 and is plugged into the switch for Subnet B. RRAS is installed on this router server and Lan Routing has been setup, but nothing else.


I also have a second subnet (Subnet B). In this subnet we have a server 2k3 machine that is going to be acting as a DHCP Relay. It's not a member server, it only has RRAS with Lan Routing and a DHCP Relay setup on it. This server is set to 192.168.1.3/24.


So to sumarise, I have two pysically seperate subnets (A & B). Each subnet is on an different Class C IP range. There is a router with 2 NIC's attached to each subnet. On subnet A we have a DC + clients, and on subnet B we have a DHCP Relay + clients.


So my question / problem is this. I can't get the DHCP Relay on subnet B to work properly. I'm not sure if I have setup the lab properly to start with. I think I should probably define some static routes on the Router server, but I'm not sure the best way to do this as I'm not fully up on this subject yet. I have had some success in that I have actually managed to get DHCP Discover packets to the DC on subnet A. That's as far as things have gotten though, Dicover packets are crossing the router, Offer's don't seem to be going back.

As far as I know it shouldn't make a difference that I'm using two different IP ranges on each subnet providing the routing is setup correctly (which I don't think it is). Should I be using the same range on B as on A?

Any advice on how to best configure this setup would be appreciated. I feel I am nearly there on getting it working but there is one thing stopping it all from working. Thanks in advance.

 

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Gonna answer my own question a little here. I have now managed to get the DHCP relay agent working.

Clients on subnet B are now able to obtain DHCP adresses from the server on subnet A. I defined a new scope on the DHCP server to offer addresses in the 192.168.1.x range and it all suddenly started working.

No static routes needed on the router server either.

I'm not sure why I needed that extra scope though. It's probably not a relavent comparison but when I was tesing VPN connections the VPN connection itself was getting an IP address from the main scope on the DC even though the VPN was coming in via a seperate NIC with an address on a completely different logical subnet range.

Anyway, I'm pretty chuffed I got it working as I feel that I have learnt quite a lot from setting it up in the first place.

I have also just managed to get a workstation on the B subnet to join to the domain on the A subnet. Thought that was quite cool, given that it's on a seperate physical and logical subnet range.

 

Good stuff Modey, i was going suggest you needed to create a scope on the DHCP server to serve the remote subnet but you have it sorted now.

When i was playing with W2K server RRAR routing, i found you didn't need to create the routing table entries for subnets that are directly connected to the router, only ones that are remote. You can also use RIPv2 and OSPF if you want to get more complicated

 

Thanks blue, but it's complicated enough at the moment.