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Automatically switch to secondary DNS server when primary DNS server is down

Posted on 2006-06-22
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Last Modified: 2008-03-04
Hello,

I have two servers, one SBS 2K3 Premium, and one Win Server 2K3 Std edition.  Both servers are domain controllers.

The SBS is/was the primary DNS server, and the Win Server is the secondary DNS server.  All the DNS settings are replicating properly.  

Yesterday I had to take the SBS server offline to rebuild, so I assumed the secondary server would take over the DNS but it did not.  If I manually point our workstations to the secondary DNS server, everything works fine.  However, they do not automatically detect it.  They just keep searching for the primary DNS server?

I'm pretty sure the reverse lookup zone is setup correctly, nslookup, ping, etc have no problems.

How can I change it so the secondary DNS server is detected if the primary DNS server goes down?

Thanks for your time,
-Torrwin
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Question by:Torrwin
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by:mikeleebrla
ID: 16960880
what you explained happening is exacly the way it is supposed to work.  If none of your clients are pointed to the secondary DNS server's IP as their secondary DNS server on the NIC properties, then they will never look to the secondary DNS server.

how do you expect them to look to the secondary DNS server when it isn't set on the properties of the NIC on the DNS client machines??????

the 'detection' you are talking about is done on the DNS CLIENT end, not the server end.  So all you need to do is have all of your DNS CLIENTS point to the primary and also the secondary DNS server. If the client can't access the primary, then it will use the seconedary (this is by design).

In your situation (if you dont want to set it up properly on the client end) you could take down the primary, then go into the secondary server and give it the primary DNS servers IP as a secondary IP.  that way all of your dns clients would then point the the secondary (since the secondary would be 'listening' on both the primary and secondary DNS servers' IPs)
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by:mikeleebrla
ID: 16960893
>>If I manually point our workstations to the secondary DNS server, everything works fine.
that is how windows DNS is supposed to work,,,, you just dont have it setup correctly.  IE it is supposed to be manually set on the NIC, or set by DHCP 'manaully"
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by:Torrwin
ID: 16960969
Mikeleebrla,

>>how do you expect them to look to the secondary DNS server when it isn't set on the properties of the NIC on the DNS client machines??????

I'm pretty sure that's the question I asked you.

I realize the detection is done on the client end.  That's why I'm asking how to get the clients to detect the server change automatically...  Is there no setting in AD that does this?

Anyway, if we set the DNS settings on the client NICs it will screw up our consultants who travel.  They have their laptops set to auto detect DNS settings so that they can use any wireless network that's available to them.  If we manually set the DNS settings they won't be able to use the internet outside of the office.  No, none of them will want to change it back and forth on their own.
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mikeleebrla earned 400 total points
ID: 16961256
That's why I'm asking how to get the clients to detect the server change automatically...  Is there no setting in AD that does this?
no there isn't,,, like i said,,, proper DNS setup is for you got have the DNS client point to both the primary and secondary DNS server, that way if the dns client can't get to the primary, it will try to get the secondary.

If you have everything setup statically now, your only option is to manually properly setup every DNS client with a primary and secondary DNS server.  If you are using a DHCP server, you can just do this one time on the DHCP server.

>>Anyway, if we set the DNS settings on the client NICs it will screw up our consultants who travel.They have their laptops set to auto detect DNS settings so that >>they can use any wireless network that's available to them.
well then just setup your DHCP server to give them the proper DNS settings?????? which would be to have a primary and secondary DNS server


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by:Torrwin
ID: 16961365
Ok, the SBS server was/will be the DHCP server.

So, can you have more than one DHCP server?  And if so, what do the clients do when the primary goes down?
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by:mikeleebrla
ID: 16961432
hold up,,, do you have a DHCP server now?  If you do, just set it up properly and there is no need to create another one.

yes you can have more than one DHCP server,,, but you need to understand how DHCP works.  A dhcp client sends out a broadcast and the first DHCP server that responds to that broadcast is who the DHCP client gets a DHCP address from.  So yes you can have more than one, but they both need to be configured exacly the same or else your dhcp clients will be getting different DHCP info depending on which server responded first.
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by:Torrwin
ID: 16961476
No, we don't have one for a couple of days.  It will be back up before the leases expire.

So it is possible to set up DHCP replication?
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by:bilbus
bilbus earned 100 total points
ID: 16966242
no you cant replecate dhcp

As for the clients you should set dhcp to give out both servers as their dns settings.

As for the servers make sure the servers have both dns servers in their ip settings tab
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