The local security authority is unable to obtain an RPC

We are in the middle of a single forest migration, where we are consolidating 4 forests to 1. My issue is with one of the forests... It struggles to create trusts with the new forest and child domains.

The troublesome forest we can call Forest T, and the domain/forest we're trying to two way trust with A.

Both DC's in question are Windows 2003 Std Server SP2, the DC of Forest A is a R2 edition box.

Regardless of which direction i attempt to build the two trust in, I get an error stating:

"The local security authority is unable to obtain an RPC
connection to the Domain controller <REMOTE DC>."

For the record, none of the DC's in question are VM's. The VPN between the two sites is wide open, and furthermore i tested to see if I can telnet from either side on 445 135 389 and 88... and i can.

Whats the problem? Whats causing the RPC connection to fail? Any advice, comments, or ideas would be very welcome at this point.

Frustrated in Texas.

Who is Participating?
Michael PfisterConnect With a Mentor Commented:
Download PortQueryUI from

and let it run on one side and point it to server on the other side and vice versa. It tests more than a telnet can do.

If this doesn't show where the problem lies, you have to further troubleshoot it by installing a network sniffin tool on both ends, i.e. Wireshark ( and check if the entire traffic is passing your VPN/routers.

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