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If DC goes down, how clients will automatically go to ADC

Posted on 2009-07-10
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Last Modified: 2012-05-07
Hi All,

I have a DC environment in which i am also running an AD integrated DNS.

Just to add redundancy i added one more ADC in the current environment and joined it to the existing domain while running the setup of dcpromo. Active directry database on the DC was successfully replicated on the ADC and i can see all the objects in ADC. Then i installed DNS on ADC, and it also gets synchronized with the master DNS at DC, getting all the DNS records from there.

Now, i am confused that how can i add redundancy at client end. If DC goes down, how clients will automatically go to ADC.
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Question by:mahtab786_dbi
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by:flyingsky
flyingsky earned 50 total points
ID: 24826761
I don't quite get it. Do you mean you just added another Domain Controller to the domain, or you mean you added an Active Directory Connector?
If you just added another DC, then all you need to do is to configure the new DC in your DHCP as a secondary DNS server. You may need to consider set it up as another DHCP server though
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by:craigothy
craigothy earned 100 total points
ID: 24826767
Basically, you just need to make sure you hand out a secondary DNS server (of your newly created DC) to all of your clients either statically or by updating your DHCP scope options.  
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by:Mike Kline
Mike Kline earned 200 total points
ID: 24826803
In addition to the DNS settings that craig and flying mentioned make sure to make the new DC a global catalog server too.
If you want the down and dirty details of how domain controllers are located take a look at
http://support.microsoft.com/kb/247811
How Domain Controllers Are Located in Windows
Thanks
Mike
 
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Author Comment

by:mahtab786_dbi
ID: 24826853
Hi mike,
I am agree with u to make the new dc a gcs...so if main(first) dc will be down..clients will go automatically to another DC...
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by:Mike Kline
Mike Kline earned 200 total points
ID: 24826896
Yes but you have to make sure to add the new DC /DNS server as their secondary DNS server like the other guys mentioned.
You can test this out during your next patching cycle.  (because I know the machine will need to be rebooted anyway)
Patch the first one and shut it down.  Make sure you can login from a few machines.  Just so you know it works.  Then power it back on.
Thanks
Mike
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by:craigothy
craigothy earned 100 total points
ID: 24826914
One other thing I would suggest in case you haven't do so already, is to make DC1's primary DNS server itself and the secondary as DC2.  Also, on DC2 make its primary DNS server itself and its secondary DC1.  That way DC1 will still be able to resolve DNS itself in the case that DC2 is offline and vice versa.
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Author Comment

by:mahtab786_dbi
ID: 24826972
ok fine.........now I have 2 doubt.........first as I mentioned in my question i have installed DNS on another DC, and it also gets synchronized with the master DNS at DC, getting all the DNS records from there.so no need to do more with dns on another dc.

second thing how clients will get IP Address as DHCP is configured on First DC.
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by:amichaell
ID: 24827246
Utilize two DHCP servers with their own scopes making sure the scopes do not overlap in regards to the IPs they hand out.  So, SERVER1 might hand out 172.17.70.0/24 addresses while SERVER2 might hand out 172.17.30.0/24 addresses.
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by:Mike Kline
ID: 24827352
If you do go with another DHCP server you can also go with a 80/20 or 70/30 split
http://technet.microsoft.com/en-us/library/cc958936.aspx
How long are your leases set for right now?  If it is the default of 8 then clients have some time before you have to worry about that.  
Yes with AD integrated DNS the info gets replicated
 
Thanks
Mike
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by:
KCTS earned 150 total points
ID: 24828408
You are on the right lines
If you have Installed Active Directory on the new Machine then if you add the DNS server role, then DNS will be automatically replicated

You MUST make sure BOTH DCs are Global Catalog Servers

If you are using DHCP then the simplest way to configure this is to set-up and authoirise both machines as DHCP servers and configure
each server with non-overlapping roles eg set one DHCP server to use IPs 192.186.1.100 - 192.168.1.150 and the other to use 192.186.1.151 - 192.168.1.200

You must also configure clients to use one machine as the preferred DNS server and the other as the alternate DNS server, for machines with static IPs you can the DNS servers in the TCP/IP properties. for machines that use DHCP, then you need to add both DNS servers DNS server options in the DHCP console - on both DHCP servers.

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Expert Comment

by:AhmedCharania
ID: 24829378
In case of primary DC down, you will need to transfer FMSO roles to newly added DC.
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