Woah, there. What you're saying contradicts itself. You say "single subnet" in one point, but then "VLAN each site" in the second point. Then you say "the networks will NOT be routed". Are you sure you know what you're saying here?
Typically 802.1q VLANs are deployed in a one-to-one relationship with IP subnets. Each 802.1q VLAN acts as an independent Ethernet broadcast domain and, as such, broadcasts from one VLAN (like, say, a machine ARP'ing for another machine in the local subnet) won't be forwarded between the VLANs. Splitting a single IP subnet across multiple VLANs requires a "smart" bridge that can do proxy ARP.
How are you planning to get ARP to work between these various VLANs?
If you really want to eliminate "cross-site 'chatter'" then what you really want is a subnet for each physical location, a router at each location connected to the "MAN" to route traffic to the other locations, and "ip-helper" functionality in each router to forward DHCP requests from the various locations to the central DHCP server.
What it sounds like you don't want is a single big subnet with a bunch of bridges running proxy ARP, in my opinion. Your DHCP inquiry really, really speaks to an underlying desire (though you don't know it) to have per-location subnets with DHCP scopes for each.
To speak to your question specifically re: DHCP: A DHCP "scope" is a range of IP addresses and options that a DHCP server will "hand out". The DHCP server chooses the scope to choose an address based on either the network interface the request is received from (if it's a broadcast request) or the address of the DHCP relay agent (if it's a relayed request).
Some background: Best way to segment traffic, VLAN or subnet?
Yes its possible, but a better solution is to have a single interface, especially on a Domain Controller, and configure your routers to forward the DHCP broadcast from the clients to the DHCP Server. In Cisco terminology this is called an IP Helper. It's also commonly referred to as DHCP Relay.
What are you going to do when you get a third subnet? What about a 10th subnet? You can't keep adding interfaces.
Best Answer
There's an official Technet guide for this that I'd use, rather than that one.
The process below is a "merge," rather than what would normally be called an "import", and will only modify existing scopes if you import scopes that exist on the target server.
If that is the case, you'll need to selectively import scopes, instead of just using the
/allswitch. The Microsoft KB on importing/exporting specific scopes only is here.As always, it's better safe than sorry, so you don't want to do anything without some form of backup. In this case, that can be achieved by exporting the database on the target DHCP server before importing the database from the other one. That way, in the event something goes wrong, you can always "restore" the configuration by importing the original database.
Finally, I personally wouldn't bother moving ANYTHING to a Server 2003 server, because I'd be doing everything I can to get rid of or upgrade anything running a decade old OS that's already end of support. (Unless you're paying for extended support, which I doubt). It also happens to be a bit easier to migrate your DHCP database to a DHCP server running Server 2008 R2 or 2012, either through the GUI or with the use of PowerShell.. but if that's not an option, it's not an option.
This step-by-step article describes how to move a Dynamic Host Configuration Protocol (DHCP) database from a computer that is running Microsoft Windows NT Server 4.0, Microsoft Windows 2000, or Microsoft Windows Server 2003 to a computer that is running Windows Server 2003.
Note: You can use the Microsoft Windows backup utility (ntbackup.exe) to back up and restore the DHCP database on a single server. Do not use the backup utility to migrate or to move a DHCP database from one DHCP server to another.
Export the DHCP database from a server that is running Microsoft Windows Server 2003
To move a DHCP database and configuration from a server that is running Windows Server 2003 to another server that is running Windows Server 2003:
cmdin the Open box, and then click OK.netsh dhcp server export C:\dhcp.txt all, and then press ENTER.Note: You must have local administrator permissions to export the data.
Install the DHCP server service on the server that is running Windows Server 2003
To install the DHCP Server service on an existing Windows Server 2003-based computer:
Import the DHCP database
Note: You may receive an "access denied" message during this procedure if you are not a member of the Backup Operators group. If you receive an "Unable to determine the DHCP server version for server" error message, make sure that the DHCP Server service is running on the server and that the user logged on is a member of the local Administrators group.
Important: Do not use Dhcpexim.exe to import a DHCP database in Windows Server 2003. Additionally, if the target Windows 2003 server is a member server, and if you plan to promote it to a domain controller, we suggested that you perform the DHCP database migration before promoting it to a domain controller. Although you can migrate the DHCP database to a Windows 2003 domain controller, the migration to a member server will be easier because of the existence of the local administrator account.
Verify that the DHCP service is started on the Windows Server 2003-based computer. Click Start, click Run, type
cmdin the Open box, and then click OK. At the command prompt, typenetsh dhcp server import c:\dhcpdatabase.txt all, and then press ENTER, wherec:\dhcpdatabase.txtis the full path and file name of the database file that you copied to the server.Note: When you try to export a DHCP database from a Windows 2000 domain controller to a Windows Server 2003 member server of the domain, you may receive the following error message:
Error initializing and reading the service configuration - Access DeniedIf the "access is denied" error message occurs after you add the Windows Server 2003 DCHP server computer to the DHCP Admins group at the Enterprise level that is mentioned in step 4, verify that the user account that is currently used to import belongs to the local Administrators group. If the account does not belong to this group, add the account to that group, or log on as a local administrator to complete the import.
Note: If the DHCP IMPORT or EXPORT command fails for users who are not explicit members of the local Administrators group, you must apply the following hotfix on the Windows Server 2003-based computer:
Authorize the DHCP server
Click Start, point to All Programs, point to Administrative Tools, and then click DHCP.
Note: You must be logged on to the server by using an account that is a member of the Administrators group. In an Active Directory domain, you must be logged on to the server by using an account that is a member of the Enterprise Administrators group.