Windows 10 clients joined our domain recently but when I block internet access on a network switch, it takes my clients a long time to login on a domain. Can somebody check on this issue and how can I get it fixed?
Hello Hudson
The reason for the long log in time is that when you have the router and/or public DNS set on workstations, these DNS servers do not know anything about internal DNS records that workstations will look for in an Active Directory domain - so the workstation is probably looking for an internal DNS record at login time and if it is querying a public DNS server or the router, it will sit there waiting for a response - and while it sits there, you’ll get the whirly wheel during login.
So, I advise you to remove any DNS servers on your client workstations apart from SBS and to let SBS do the DHCP as well - you and your users will be so much happier! If you don’t want to let SBS do DHCP, configure your router to only hand out the SBS IP address as the DNS server, nothing else.
SBS should be set up with forwarders set to your ISP’s public DNS servers, or something like Google or OpenDNS. A client workstation with only SBS set as the DNS server will then request DNS lookups to SBS which will then forward any requests it doesn’t know about already to the forwarders you’ve set.
Hi @Hudson,
Welcome to the community, 
,
Please check if the always wait for the network at computer startup and logon policy is enabled or not? (navigate to computer configuration->administrative templates->system->logon)
or
Are you using folder redirection for user’s home directories? If so then that most likely is the cause of the issue as it is most likely trying to do a sync on boot up. If you aren’t then it could possibly be something else related to GPOs or start up tasks that rely on the corp network. Really there are a ton of reasons why this might happen so it depends on how you domain and network is setup.
If the above was not helpful then please try enabling Verbose Login for start up and shutdown. This will give you a clue as to what step in booting and shutdown are the problem. https://www.google.com/amp/www.thewindowsclub.com/enable-verbose-status-message-windows/amp
Slow logins on domain attached machines are often caused by badly configured DNS in SBS world. Have a look at this first and ensure that the client is set to dhcp which sbs should be providing. Check that the machine is pointing only to SBS for DNS.
