Have just changed ISPs and as a consequence the domain's subnet mask needed changing (or I hope it did - couldn't access the outside world until I did, anyway). Everything seemed OK on the tested machines, but once more logged on things got flakey with various machines unable to access network resources. The machines can still ping the server by IP and name, but not connect to \\server\resource (or \\192.168.xxx.x\resource) - get network resource not found or an authentication request which will only work if different credentials are input.
I've tried all sorts of things to no avail, far too many to list or remember!
Also unable to apply a new Group Policy, but suspect that this is because the machines can't see the server at logon.
I think/hope/pray that I have got this sorted (if I have, it was my sketchy knowledge of DNS that caused it :embarassed:) but do have some questions:
Where should one put ISP-provided DNS addresses?
Should the local DNS server still be in the list (for school domain names)? If so, where in the list?
The ISP DNS server IPs should be in the Forwarders tab in DNS Server.
I presume you've updated servers, printers and admin workstations which may have a static IP config? Everything else should work with DHCP Server.
Yup you should use your ISPs DNS servers as forwarders within your AD DNS servers setup. You should use your AD DNS servers as DNS servers for all of your internal machines.
I (eventually) put them in the right place, then - though it looks like I need to tweak things to match the second part of @Soulfish's answer.
Normally I could remote in to a different server and check the setup there, but as that school is the first with the new ISP that's not easy to do. Been too busy/stressed/tired to think to look at the setup at other sites!