Question : How do I join a domain over a VPN tunnel?

Here is my configuration.  I have two offices.  Each office has its own Windows 2003 server and is presently running its own domain.  I have purchased and installed two Linksys WRV54G routers which support VPN.  I have establish the VPN tunnel and that portion of this is working fine.  I can access IPs from each network across the tunnel established by the routers.  I can even hit network shares as long as I use the IPs.

What I want to do is eliminate one of the AD domains and have one combined AD domain for both locations.  I want the primary AD server located at office one and the server located at office2 as the secondary.

What I have found is that I cannot use computer names accross the network.  This does not suprise me terribly and probably has something to do with the DNS settings.

I suspect that once I get everyone on one domain, that names will work fine.

I have tried to join a desktop in the office2 lan to the domain that is controlled by the server in office1, but it cannot find the domain comtroller for that domain.

So, I guess what I am asking is how do 'take the next step' now that I have established the VPN to joining domains across the VPN tunnel?

Answer : How do I join a domain over a VPN tunnel?

your going to get downtime no matter what, as you are going to have to demote and repromote your server in the remote site

first thing first though is to get name resolution happening accross the VPN

this is some advice from robwill that i find works well

NetBIOS names are not normally broadcast over a VPN, to work around this issue try the following solutions:
1) Use the IP address (of the computer you are connecting to) when connecting to devices such as;   \\123.123.123.123\ShareName   or map a drive at a  command prompt using  
 Net  Use  U:  \\123.123.123.123\ShareName
2) An option is to use the LMHosts file which creates a table of IP's and computer names. LMHosts is located in the Windows directory under c:\Windows (or WINNT)\System32\Drivers\Etc\LMHosts.sam , instructions are included within the file. Any line starting with # is just a comment and is ignored. Open the file with Notepad and add entries for your computers as below;
192.168.0.101      CompName       #PRE
Hit enter when each line is complete (important), then save the file without a file extension. To be sure there is no extension ,when saving enclose in quotations like "LMHosts". Now when you try to connect to a computer name it should find it as it will search the LMHosts file for the record before connecting.
More details regarding LMHosts file:
http://www.microsoft.com/resources/documentation/Windows/2000/server/reskit/en-us/Default.asp?url=/resources/documentation/windows/2000/server/reskit/en-us/cnet/cnfd_lmh_QXQQ.asp
The drawback of the LMHosts file is you have to maintain a static list of computernames and IP addresses. Also if the remote end uses DHCP assigned IP's it is not a feasible option. Thus in order to be able to use computer names dynamically try to enable with some of the following options:
3) if you have a WINS server add that to the network cards configuration
4) also under the WINS configuration on the network adapter make sure NetBIOS over TCP/IP is selected
5) try adding the remote DNS server to your local DNS servers in your network card's TCP/IP configuration
6) verify your router does not have a "block NetBIOS broadcast" option enabled
7) test if you can connect with the full computer and domain name as  \\ComputerName.domain.local  If so, add the suffix DomainName.local to the DNS configuration of the virtual private adapter/connection [ right click virtual adapter | properties | TCP/IP properties | Advanced | DNS | "Append these DNS suffixes (in order)" | Add ]