Domain controller is not available

On we have  two sites  and  both  sites  have DCs. DC on one site was down and no users we're able log in.
My impression was that users will be authenticated  via other site and domain controller.
What could be the reason the users we're not able to log in?
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Michael MachieIT SupervisorCommented:
The two sites must be connected in order for that failover to occur. Are they connected via a tunnel or MPLS or in some other manner? If not, no immediate authentication will occur.
Are you able to ping and/ or RDP to the other DC?

If they are connected and accessible from both locations then either of them should have been able to authenticate Users for either location.
Will SzymkowskiSenior Solution ArchitectCommented:
There is no failover mechansim here... What you need to do is that if the DC in site 1 is down you need to point your clients in Site 1 to the DNS/DC server in Site 2. Once you have done that your users will be able to authenticate.

This is why it is a good idea to have atleast 2 DC's per site. If you cannot do that then when you need to do is add the DC from the preceeding site as a secondary DNS entry within the network adapter.

This means modifying your DNS entries for DHCP to hit all of the clients and manually doing this for all of the servers.

Site 1 = (DC)
Site 2 = (DC)

Site 1 Client  = PrimaryDNS -, Secondary
Site 2 Client = PrimaryDNS -, Secondary

With this configuration users will still be able to authenticate.

Now if you have Exchange in both Sites Exchange will not work with this scenario because it needs a read/write DC/GC in the site for it to work properly.

sara2000Author Commented:
Strange,  able to ping either way from site 1 to site 2 and tcp configuration with both site dns as alternative.
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Will SzymkowskiSenior Solution ArchitectCommented:
Yes that is good that you can PING the servers, that means there is Network communication present. This does not mean that your clients will use the alternate Site for DNS queries if it is not set in the DNS configuration on the client/server machines. You HAVE TO ADD it as a SECONDARY DNS IP for this to work, as i have illustrated in my first post.


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sara2000Author Commented:
Waiting to test the all the above .
Will SzymkowskiSenior Solution ArchitectCommented:
Ok sounds good.

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