I am new to windows server. We have three servers in a colo and all the three servers are configured with static IP's. I want to create a domain and add these three servers as members. I know how to do it if all the systems are inside a network, but our servers are not LAN connected. Can some one please point me to right direction?
I have registered a domain, that I am planning to use.
There's not going to be much difference in the implementation simply because the servers are directly connected to the internet. Take your domain controller, run DCPROMO on it, and setup the domain. Then set that server as the DNS server for the other 2 servers and join them to the domain. Pretty simple.
There's some considerations with this setup though. First of all, your DC is directly attached to the internet. I'd want to make sure you have a good hardware firewall in front of it. This can be done without NAT, but make sure it's done properly. If that server is compromised, then game over.
Another consideration is that you've just added a single point of failure. Only 1 DC means you only have 1 DNS server as well. You can try throwing DNS on another one of the servers and making sure the zone propagates properly. You're still left with only 1 DC though. So if that server fails, you lose authentication. You can promote another server but that means you have 2 DCs on the public internet to worry about.
If I were you, I'd rather skip the windows domain for now. With 3 servers, it just doesn't work out practically when you think about security and stability of your network. Maybe when you have more servers and can dedicate 2 to being DCs it will work out better.