I have a client with 4 main sites, All are connected by High speed VPN.
Each 'site' has it's own DC, and in DHCP each site has a different site as it's second DNS. So we have not needed AD sites as of yet.
We are now adding a 5th site, that will not be part os the VPN mesh, it will only be off one of the sites.
This will require setting up the sites as AD sites so they know how to talk to the 5th one.
My worry / question is, When I have setup sites before, with only 1 AD in each site, when the AD goes down, the site goes down, the machines seem to stop looking at the other sites as backup.
Am I missing something that allows sites to stills goto another site's AD? Is there a better way to set up the sites?
Also, what happens when a machine not in any defined sites' IP range comes along, does it go to any site?
The docs I can find online are either too simplistic, or way to detailed to answer these questions.