Hello, I was wondering when setting up sites in Active Directory, do the subnets have to contiguous or can sites have any network assigned to them? Also, to configure a DHCP scope, do the subnets have to be contiguous? I seem to recall that for both of my questions, it is Microsoft best practice to have contiguous subnets no matter what you do. I just can't seem to find an answer online or in my textbooks...

The answer is No to both of your questions. You may have read that with regard to routing in general. The reason is as follows. Say you have two buildings...10.1.x.x in one and 10.2.x.x in another. Say there is a router in each building handling all of the subnets for that building. The routing tables for each router will be small and efficient because the router doesnt need to know about every subnet in the remote building. For example, if you are in building 1 and need to send packets to building two, if the destination subnet is for example, 10.2.5.x/24, the router will just send it to building 2 without knowing about the specific subnets. It just knows that all subnets within 10.2.x.x/16 go to building 2. Now if you just had random subnets, routing will still work in the same manner, but in this scenario, you would have to define each subnet on both routers. Say these buildings have a 100 floors each, with each floor having one subnet. The routing table has an 100 routes for the remote subnet that isnt needed. Now picture a scenario where you have 100 buildings with 100 floors each...the routing table will be huge if you had random subnets all over the place. Guides and tutorials, visit ITGeared.com.

The answer is No to both of your questions. You may have read that with regard to routing in general. The reason is as follows. Say you have two buildings...10.1.x.x in one and 10.2.x.x in another. Say there is a router in each building handling all of the subnets for that building. The routing tables for each router will be small and efficient because the router doesnt need to know about every subnet in the remote building. For example, if you are in building 1 and need to send packets to building two, if the destination subnet is for example, 10.2.5.x/24, the router will just send it to building 2 without knowing about the specific subnets. It just knows that all subnets within 10.2.x.x/16 go to building 2. Now if you just had random subnets, routing will still work in the same manner, but in this scenario, you would have to define each subnet on both routers. Say these buildings have a 100 floors each, with each floor having one subnet. The routing table has an 100 routes for the remote subnet that isnt needed. Now picture a scenario where you have 100 buildings with 100 floors each...the routing table will be huge if you had random subnets all over the place. Guides and tutorials, visit ITGeared.com.

Great! Thank you very much! That's just the answer I was looking for. I noticed that I forgot to type a word though for my second question. To configure a DHCP SPLIT scope, do the subnets have to contigious?

So with the DHCP Split scope concept, you are taking one scope and splitting the available leases between two DHCP servers. From a management perspective, you are managing one scope. If you add more scopes on both servers, the same rules apply that I previously discussed. They do not have to be contigious. Here is more information about split scopes: Load Balancing Using Split ScopesGuides and tutorials, visit ITGeared.com.

Thanks again! Your replies were very helpful and appreciated :)