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eugene20022002Flag for South Africa

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1 DHCP server supplying 2 subnets

Good day Experts

My current setup:

I have 3 domains , domain A , domain B , and domain C
Domain A is on subnet 1 and domain B and C is on the other subnet.
Im running Windows 2008 on all DCs
One member server running Windows 2003 which has been identified as the dhcp server.

Desired outcome:

I would like to setup 2 DHCP servers to supply these two subnets.
Unfortunatly this is how I inherited the infrastructure and would not have done it like this myself but unfortunatly its too late to change the entire network infrastructure.
There is one router between the two configured to relay dhcp traffic.

Question:

How can I setup a DHCP server to supply both subnets. each subnet getting its own dns servers , routers , domain suffix/name etc..


Please let me know should you requred additional information.


Thanks
Eugene
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Discusfish
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Hi Eugene - in one part of the question, you ask about setting up 2 DHCP servers, and in the other you only want to use one - which do you actually want?

I suspect to make this work, you're going to need to collect the MAC address of each network card in order that the DHCP server can supply the right credentials to the right machines. With 3 DHCP servers, it becomes fairly trivial.
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@Discusfish > Sorry for the confusion. I would ideally want to use 2. each holding 50% of the address to build some type of fault tolerance in, but if that is not possible one server would be fine aswell. basically which ever would work, 2 or 1
@Netcraft:>  
Looks like SuperScopes is the way to go. BUT!
How will a client know which scope to get its details from?
For example if a client belongs to domain A and it contacts the DHCP server, I would like to have the domain A settings specified , example dns of domain A , domain name etc.

I need some more detailed instructions.
Anything in particular to be careful of or to take note of?
i just did a test.
I setup 2 scopes with each having their own details.
Then setup a superscope and added those 2 scopes.
The problem I had was that they did not get addresses from the scope I had hoped.

How do I move on from here? Do you require more info?
Does you router provide relay?
From my understanding of DHCP, it's the server that has to "know" which scope to apply to a particular MAC address - so, you'd have to know all the MAC addresses using Domain A, B and C and then assign those MAC addresses to the relevant scope(s).
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DHCP will assign a lease (within a superscope) based on the IP address of the relay. It doesn't need to have a pre-defined list of MAC addresses to grant a lease.

How have you configured the Relay Agents?

And how have you configured the Scopes within the Superscope?

Regarding DNS based on the domain. That just won't happen unless you have a static reservation and alternate DNS assignment for every system within "the other" domain. A DHCP server will not, at least without extra software / hardware, hand out leases based on domain membership.

Chris
Incidentally, if a machine has an IP address, you can ping it and then use arp -a to find it's MAC (physical) address.

If you want some control over what MACs are allowed to use DHCP (handy for preventing random devices from getting DHCP information) this is handy: http://www.petri.co.il/filter-mac-address-windows-server-2008-dhcp-server-callout-dll.htm
I wish my scenario wasnt so complicated because I've setup quite a few DHCP servers before and all of them was pretty easy, but this time I dont know what they were thinking when they setup the network.

Anyway, I do not have access to the router, its run by a 3rd party company and wont give access. All I know is that when I setup a DHCP server (2 scopes in one superscope) It gives IP's from the one scope first and then only from the other once the first scope is depleted.

With regards to the relay agent I cant aswer that with certainty all I know is that once I authorise the DHCP with a couple test addresses, I can pick up IPs from both sides of the router.
Whats bothering me tho is that if I for example setup a test machine on the left side (refer to picture) on the 111 subnet and a gateway of 111.1 I can still connect to everything when I think Im not suppose to. Does that complicate things even further?

Thanks again for all your assistance!

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Thanks Chris.

I will have a look at wireshark and filter some dhcp requests.
Its going to take me a few days but will get back as soon as I have some valid feedback.

No problem, whenever you're ready.

Chris
Hi

Looks like the initial tests are going well.
I have 2 scopes now within a superscope.
Unfortunately I couldnt get the part of sorted, but I seup things so that it doesnt matter what address they got. DNS is intergrated so it doesnt matter what dns they point to.

Will be putting more and more on slowly as things go by.
I just created a GP for the diffferent domains to get the dns suffix search list.

Sounds good so far :)

Chris
Was pointed in the right direction.