clients not able to login with unspecified error

I have taken over maintaining an osx server with little experience in servers (I installed and run a ClearOS internet gateway at home & use limited functionality but I'm not a networking/server expert & have no formal training!).

Some time ago we started having problems with the server (10.5 running on High Sierra) which started when we had not made any changes to the server & we assume was due to some automatic update. Clients either cannot find the server or if they can there is a login failure with a very vague message about an error but no details about what the error is. Should I expect to find a message in an error log file when that happens & which log?

If my memory is correct the problem started on a previous version of macos & we upgraded to see if it would solve the problem - it didn't & we put it on the back burner but we now have a more pressing need to have an operational OD server. Initially DHCP & DNS were running on the same host as OD server. Recently we have installed a Cyberhound server which now provides DHCP & DNS to the network. That didn't fix the problem. I've also then tried fowarding DNS requests for the host from the Cyberhound server back to the host with the host now being the DNS server for itself (which is how it is currently operating). Based on what I have read the problem is likely to be DNS related.

I can ping the IP address of the server (, the name of the host (stserver2.local) and the name of the OD server (stserver2.mccs.lan).

Which then raises the issue that the host and OD server have different names. I'm not sure why they would be different & don't know if it matters (or whether they must be different). I assume both names must have records on the DNS server but assume that both cannot have reverse DNS records as I don't think is would make sense for the one IP address to have two entries. Which name should the reverse dns lookup point to, the host or the OD server? My guess is the host.

Any suggestions would be most appreciated!