example : First Forest (with domain : domain1.net -> 192.168.1.0) Second Forest (with domain : domain2.org -> 192.168.1.0)
You can't have the same IP address on the same physical network segment twice. This would cause a duplicate error and only the first one up and running would work. (ie: the second PC to boot would give the dupe error and not be able to connect to the network)
You could likely have two separate forests sharing the same physical network and same subnet....as long as each attached client/server/printer etc had a unique IP address. The thing is, this would be rather confusing and in my opinion, it would make sense (well, to me anyway) to separate them by subnet as well as name.
We have two different forests on the same wire (first -> 10.10.1.0 and second -> 100.100.100.0)we also have a router to the internet with IP -> 10.10.1.1 and we want the second domain with 100.100.100.0 to access the internet from the router (10.10.1.1). How can we do that? With routing? And sometinhg else.. will there be a conflict with the two PDCs? no.. right?
Yes you can do that with routing. You would have to setup static routes on your router in order for both subnets to be able to:
a) access the internet through your single router (gateway)
b) access the other network (subnet).
Will there be a conflict with the two PDC's? No, since there are no PDC's in an Active Directory environment. There is a PDC Emulator FSMO role but that's not the same thing. There shouldn't be any conflict between the two different DC's and their forests as long as they have differen't IP's and different domain names.
If I might comment....
I'm not sure what you're trying to achieve here and perhaps some explanation would help us help you. But know that multiple subnets can, and frequently, do indeed inhabit the same physical network.
The fact that you called a DC (domain controller) a "PDC" (which btw, is Windows NT 4.0 nomenclature and stands for Primary Domain Controller) tells me you need to do a lot more learning on the topic of Windows Active Directory based domains.
