Domain and sub domains

So I'm building a network from scratch with Windows Server 2003 & Exchange Server 2003.  My plan is for my domains to be:

This relates to a question I asked in the past.  So that when I setup exchange, all these networks share the same GAL.  What is the best way to achieve this?

Do I need a server setup as a root domain at and setup the other's as child domains?  If that is the case, is it possible to setup the root domain, and a subdomain on the same server?  I have to keep the macines I use to a minimum.  Perhaps I'm going at this wrong, and this has to do with configuring DNS differently.  

In the past I had configured 3 different domains in their own forest, but this didn't allow me to share their GAL.  Thats the ultimate goal here.  To have the 3 unique domains but all having the same GAL.

Please advise on the best way forward.
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Leon FesterConnect With a Mentor Senior Solutions ArchitectCommented:
You need at least 1 DC for each domain.
No DC = No Authentication = No Domain

You configure DNS locally for each domain/DC
You enable DNS Zone replication to all the Domain Controllers in the forest.

Why? because AD is dependant on DNS, so ideally you want your domain to function even if other DNS servers/domains are having problems.

The easiest way you'll get to your design:

Would be by creating the forest with a root domain and the 3 child domains. (x4 DC's)

I'm not sure what DNS naming conventions you're worried about...please elaborate.
Are your domains going to be trusted? One way, two way, etc...?

look at this article -
usmcguyAuthor Commented:
The domains will be trusted both ways.

I've read about IIFP in the past.  But is it the best way to go?  I was thinking that if you built your forest/domain correctly, you wouldn't need to go that route.  Am I wrong?  If not, the piece I'm missing is knowing how to setup the forest/domain correctly.  Otherwise, I would just have to setup 3 seperate forests, and use IIFP.
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Leon FesterSenior Solutions ArchitectCommented:
You don't need IIFP.

You will be running an Active Directory forest so all domains are linked.
With Exchange 2003 you can only have one Exchange Organization in the forest.
This can be achieve simply be configuring Exchange for "Using a Single Forest Topology"

Read the following:
usmcguyAuthor Commented:
Yes, this is correct. But my question remains, would I need a dc at the root of the forest hosting my Or could a dc hosting one of the other domains (aaa, bbb, or ccc) also be at the root of the forest and still maintain the DNS naming convention.
I ask because I have to keep servers use at a minimum
usmcguyAuthor Commented:
You pretty much answered my question.  I was more curious if there was a way to setup the forest without having to setup a domain at first.  But as I suspected, this isn't possible.  Thanks for the input!
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