We're a small web development company. Our domain has two DCs: a main one (BEEHIVE, in the datacenter and a second one (SPHERE2, in the office. The office is connected to the datacenter via a VPN.

We recently had a brief network outage in the office. During this outage, we weren't able to access the domain from our office machines. I had hoped that they would fail over to the DC in the office, but that didn't happen. So I'm trying to figure out why. I'm not an expert on Active Directory so maybe I'm missing something obvious.

Both domain controllers are running a DNS server. Each office workstation is configured to use the datacenter DC as its primary DNS server, and the office DC as its secondary:

  DNS Servers . . . . . . . . . . . :

Both DNS servers are working, and both domain controllers are working (at least, I can connect to them both using AD Users + Computers).

Here are the SRV records that point to the domain controllers (I've changed the domain name but I've left the rest alone):

Default Server:  beehive.ourcorp.com

> set type=srv
> _ldap._tcp.ourcorp.com
Server:  beehive.ourcorp.com

_ldap._tcp.ourcorp.com  SRV service location:
          priority       = 0
          weight         = 100
          port           = 389
          svr hostname   = beehive.ourcorp.com
_ldap._tcp.ourcorp.com  SRV service location:
          priority       = 0
          weight         = 100
          port           = 389
          svr hostname   = sphere2.ourcorp.com
beehive.ourcorp.com     internet address =
sphere2.ourcorp.com     internet address =

Does anyone have any ideas?


  • An obvious and perhaps silly, but necessary question: Did the outage affect connectivity to the 10.x.x.x subnet? From what I'm seeing if fell off the network but remained reachable to clients you should have seen logons being processed by Jun 3, 2009 at 18:21
  • Thanks Evan - yes, the 10.x.x.x network is all in the office and it remained reachable during the outage. Jun 3, 2009 at 18:48
  • Can you be more specific as to what you mean by site boundaries??
    – user70200
    May 3, 2010 at 1:04

2 Answers 2


Check to make sure that BOTH are Global Catalogs.


1.) Open Active Directory Sites and Services.

2.) Scroll down, expand the site that your DC's are in. Expand

3.) Expand each of your DC's so that they're showing `NTDS Settings'.

4.) Right-click on 'NTDS Settings', select `Properties'.

5.) Ensure that the `Global Catalog' checkbox on each is checked.


I'm assuming that you've already checked your replication, made sure everything else is working properly, etc. This is intended to be a quick-check option.

  • 1
    Thank you Greg. You were right, the domain controller in the office is not a global catalog server. I didn't realize that would prevent logins to the same domain from working. (We do have a separate domain for our production servers, but we had problems just accessing other machines in the same corporate domain as the workstations.) Jun 3, 2009 at 19:00
  • I think the reason we didn't make the office DC a global catalog was because we didn't want our Exchange server in the datacenter reaching out to it. If I recall correctly, Exchange selects a GC automatically and we can't force it to choose a particular one. We didn't want it to reach out over the Internet to our office unnecessarily. But the problem is that we don't have sites set up, as Jim mentioned... Thanks, Richard Jun 3, 2009 at 19:02
  • np mate! Glad I could help! Jun 3, 2009 at 19:17
  • Exchange will try to reach a GC that is close to it - you can define in AD which ip addresses are i n which site, and that goesi nto a lot of selections (file shares, dc) trying to stay in the same site.
    – TomTom
    May 3, 2010 at 5:18

My wild guess is your site boundaries are wrong.

  • You're right, our sites are a problem. We only have "Default-First-Site-Name" for the whole domain, even though the office and the datacenter are not connected by a high-bandwidth link. (It's around 1 megabit.) We inherited this infrastructure from someone who's no longer here, and there is definitely some cleanup to do. I hadn't expected the site boundaries to cause problems connecting to a DC, but like I said I'm definitely not an expert. Thanks, Richard Jun 3, 2009 at 19:05

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