Simple problem there my friend – both domains are currently on the same subnet (Network Range). The 255.0.0.0 (/8) you mentioned can be “subnetted” to smaller chunks that will solve the issue you’re having.
From what you’ve posted, a good option is to change your subnet mask to a /24 (255.255.255.0):
Domain 1 = 10.128.101.x 255.255.255.0
Domain 2 = 10.129.102.x 255.255.255.0
Then all you will need is to ensure that you have IP routing set up (if you want the two subnets to be able to communicate with each other.) I know Windows server can be configured to do some simple routing within itself – Good “how-to” from Microsoft.com