Windows

Did they ever log on to the BDC? One thing I seem to remember is that workstations will log into whichever domain controller that last validated them (sort of like they create a secure channel to it).

We have a PDC in New York and a BDC in Massachusetts. When I find my users consistently logging on via the PDC, restarting and trying again usually gets them the BDC.

You can stop the server service on the PDC and try to logon with a client, look if they get validated. Its also possible that the server service is not working properly on the bdc. Question: what operating system are using the clients. You can also check the event log after manualy try to sync the domain.

Good luck.

You may want to make sure that the PDC is reachable by the BDC and vice versa.

To add a BDC to a domain, the PDC has to be contactable. Therefore the first task is to check that communications are working.

If you are using TCP/IP then ensure you can PING the PDC,

ping <ip address of the PDC>

If this is OK then the problem is at the NetBIOS level. If you have WINS on the network ensure the BDC is configured to use the WINS server as when the PDC starts it will register the WINS name <domain><1Bh> which is used to identify the domain controller.

Alternatively the LMHOSTS file can be updated.

Start Notepad
Open the file <systemroot>\system32\drivers\etc\lmhosts
Add a line with the following syntax
<IP address> <machine name> #PRE #DOM:<domain name>
Save the file
To use the lmhosts file during installation you should create the file on another machine and copy it over when the BDC is being installed.

Try this and we'll take it from there. . .

You don't say how you are doing NetBIOS name resolution. If you're using a WINS server and WINS is on the PDC only, this may be why the clients are always contacting the PDC first and logging on there. They have to get to the PDC for name resolution anyway, and then since they've already found the PDC they will use it as their logon server. One thing to try would be to set up WINS on the BDC as a replication partner with the PDC. Then, set your clients in location 2 to use the BDC as their primary WINS server instead of going to the PDC directly for name resolution. You could also solve this with an LMHOSTS file, as suggested by others, but I'm not a fan of static name resolution unless you have to. Hope this helps!

Is the BDC able to synchronize with PDC via WAN ?
One thing you should check on this is the NetBIOS Scope ID on the BDC.

Let me know.