I have a multi-forest Active Directory environment with a 1-way trust between them. (Forest B trusts Forest A.)
Domain controllers in Forest A report event ID 5807 from source NETLOGON, which indicates that
"there have been nn connections to this Domain Controller from client machines whose IP addresses don't map to any of the existing sites in the enterprise. Those clients, therefore, have undefined sites and may connect to any Domain Controller including those that are in far distant locations from the clients. A client's site is determined by the mapping of its subnet to one of the existing sites."
This is because the servers from Forest B are in subnets that are not defined in the "AD Sites and Services" subnet configuration of Forest A.
Is there any way to tell all authentication requests from a remote forest to use domain controllers in a specific Active Directory site? It doesn't seem to make complete sense to list Forest B's subnets within Forest A's Active Directory Sites and Services configuration...but perhaps that is the answer?