How do I prepare local domain controller for uplink outage

Question

My site will be losing connectivity to the rest of the network for a few days up to a week. When we've had outages before I find we get delays browsing local shares and very long delays logging in. Is there something I can do to tell the local controller to work in "standalone" mode for a while?

Answer 1

A few ideas.

1. Make sure all clients at the site that will experience the "outage" are using domain controllers at their own local site as DNS resolvers. DNS timeouts add little delays to everything that add up to excruciating wait times. The domain controllers at the disconnected site, in addition, should not be forwarding DNS queries to the other domain controllers in other sites. (Instead, they should be forwarding to your ISPs DNS servers, or at least something like Google's public DNS. This is just so internet browsing is still fast.) Also, the DNS resolvers of the domain controllers themselves should point only to other domain controllers within their own site - not to other domain controllers in other sites.

2. Configure AD Sites & Services correctly so that the subnet object in AD corresponding to the actual network segment that the computers are on is associated with the domain controllers in the same site. This is how client computers know how to efficiently locate a domain controller in their own site. (Or the next closest site, but that's outside the scope of this discussion.) This is also how DFS knows how to make correct referrals.

3. If mapped resources reside outside of the affected site, then use Group Policy (linked to the Site, perhaps,) to wipe out all client drive mappings. The clients will not be able to access the resources anyway, so just wipe them out. However, if you have time to prepare ahead, then consider not using mapped drive letters at all because that is an ancient technology. Instead, use DFS. Network mappings don't have to be associated with drive letters - mappings can just be a folder called "Corporate" and the user clicks the folder "Corporate" and it targets a network location such as \\contoso.com\Corporate and it just works because that will be a DFS namespace and clients will be served referrals to the correct file server (the one in their own site) because AD/DFS == Magic.

4. Or at least, use BranchCache if not going DFS. Sorry, just can't recommend in this scenario.

But again, both DFS and BranchCache require infrastructure changes that require to have already planned ahead.