At my workplace we have a Windows Small Business Server, which runs DHCP and DNS services for our local network. I believe it's an Active Directory setup, but since I have no clue of Windows really, I'm not entirely sure about this. What I can say is that the server controls a Windows domain, and some of our Windows machines are in that domain. We have loads more computers, for our clients to use, and those are plain Internet PCs, running Windows but not attached to a domain or workgroup.
We often have problems with the server machine, partly because the hardware is fairly old. Also, the firewall/router device we are using is often causing trouble. I'm replacing the latter now with an old PC running Linux and a firewall system (OpenWRT).
It is very important that our clients have working Internet connections, and in the old setup a failure of either the router/firewall or the Small Business Server would mean that they do not. While I'm replacing the old firewall with my Linux system, I also want to migrate the DHCP and DNS services from the server to the firewall. Therefore, a failure of the server would no longer cause Internet problems.
Now I have installed the new firewall. I have switched off the DHCP server on the SBS, and I have configured its TCP/IP protocol such that it uses the new firewall machine as DNS. Everything worked like a charm, but only for a few hours. I tested a few Windows computer on the domain, and they worked. I disabled and enabled the network interface, to obtain the network config from the new DHCP service (the one on the firewall).
However, after a few hours (i.e. this morning when I came back to work) the Windows machines on the domain could not mount network shares anymore. Network drives and also printers refused to work. When double-clicking a network drive, an alert box popped up saying "The local device name is already in use".
What do I have to do to keep our Windows network services functioning when deactivating the DHCP server on the SBS and operating a DHCP on a separate (non-Windows) machine?
So far, I have added DHCP options on the new firewall, referring to the IP address of the SBS as netbios-ns and netbios-dd. That does not seem to be enough.
I would like a setup, where the firewall operates local DHCP and DNS services, but the Windows PCs know that the Windows services are available from a different server. Anything regarding Windows network shares, printers, Active Directory, whatever, should be done by the SBS, which is not the acting DHCP and DNS server.