I have one domain which has 3 physical geographical locations on different subnets. Users were complaining about length of time to authenticate so i split them into 3 sites under ad sites and services and linked the subnets and locations to each site. However i am not sure it has made much difference as some users are still getting authenticated a different site to which they belong. Also under ntds settings i am not sure which servers to replicate to which. I have 2 dc's in the main site which replicate to each other (automatically generated). I have 1 dc in each of the other sites should i just add 1 server at each of the other sites to replicate with?.