One question, why do you want to name your domains this way? It seems that you have a small network and you probably want to keep it as simple as possible.

You can make just one Active Directory which spans both sites. Just specify your subnets and intersite transports in Active Directory Sites and Services mmc module so that replication works. Then you can have just

example.com

Active Directory domain, with different sites in the AD, and Organizational Units for each of the sites if you need to get fancy with rights, and group policy.


If you are talking just about dns, sure, you can do what you want. But, if you mean Active directory as well, a single server can only host one Active Directory Domain. so, if the server in city one hosts

example.com for a domain, it cannot also host city1.example.com

You could call the forest in which these domains live

example.com

with the domains

city1.example.com etc.

Or you could make two domains city1.example.com and city2.example.com and create a trust relationship without having them both in the same forest(would be better if they were just in the same forest).

Or you could just make one domain and seperate the rights and such using Organizational units and group policy.

I have got an Active Directory domain which spans 8 offices all in "example.com".