I recently did some testing using KxRPC.
I have a test domain with three domain controllers. Only one of the domain controllers has the KxRPC service running.. the other two I turned off the netlogon service (thinking that if only the one domain controller was the actual logon server that it would also be the only one which kixtart requests RPC information from...) -- This was NOT the case.

It would seemingly randomly pick whichever domain controller it felt like to obtain RPC information. So I added a file:

kixtart.ini to my netlogon root with the following (where "MIS" was the domain controller for the domain "MIS_CORP":

[KXRPCMapping]
;MyDomain=\\MyServer1,\\MyServer2,\\MyServer3
MIS_CORP=\\MIS
;Default=\\ServerA,\\ServerB

and guess what-- no more failed RPC .. it obtains RPC information perfectly now for every single logon since I changed that.
IF you look in the manual, Ruud talks about a couple other ways to specify which servers should be the RPC servers (registry etc..) I happen to like this way because I can set it up for multiple domains and stick it in the general replication path and I'm all done.

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