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DNS question with SBS 2008

wouterkcs asked
Medium Priority
Last Modified: 2012-05-06
We having problems that users are frozen with the internet when the SBS server is not available.

I belief it has to do with the fact that the the clients network properties (via DHCP)points the DNS to the SBS server -- which is down so it can resolve the DNS solution.

Is there a way around this??

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Add the ISP's DNS server as a seconday DNS server.  Just add it to the DHCP scope.

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Toni UranjekConsultant/Trainer

It's bad idea to configure DNS setting on client in domain to use anything else than internal DNS. You will have difficulties accessing domain controller. Proper solution would be to add second DC/DNS to your environment.

If you add a 2nd DNS server as suggested by DMTechGroup, and ensure it's Secondary, as he suggested, then as long as your DNS server is up, it will be utilized, and if it is down, then the alternate/2ndary/ISPs will be used.

Active Directory relies on DNS, so it is critical that the primary is the one utilized by AD.  However, you may not have time to set up a 2nd dc/dns as Toniur suggests, and if you need a quick fix, DMTechGroups works.
It's an SBS server so it is most likely a small network, would be a waste of resources to add a 2nd DC to this.  Chances of the server being down is most likely low so adding a 2nd DNS from the ISP should have almost no effect on the operation of the network.
Toni UranjekConsultant/Trainer

Unfortunately, using external DNS on on internal network with AD, alwyas has effect on clients. When preferred DNS server goes down, clients will begin to use alternate DNS, which will fail to resolve all AD related DNS quieries. And again unfortunately, clients will not stop using alternate DNS and begin using preferred DNS until they are restarted or you use Vista.
I understand that.. but in the end does the cost justify the end result.  I am sure it is much easier to reboot up to 25 computers after a server startup.  If the SBS server is down then I would think it is safe to assume no AD inquiries are going to be needed during that time anyhow.
Toni UranjekConsultant/Trainer

Assumptions is mother of all...

Unfortunately, clients query for SRV resource records more often then one would think.

Would a redundant dc/dns server be a good idea?  Sure.  But if you read the guy's issue -- his users have no internet access, and he wants to fix THAT.  He knows his server is down.  He's not asking how to add redundancy or avoid it in the future.  The answer to that is pretty obvious.  He's asking for the best way to get his users up NOW.

I don't know about you, but if I told someone in this situation, that the best solution was to go buy another server, I wouldn't be brought back for more consulting.

1) Fix the current problem
2) Suggest solutions to avoid it happening again in the future, advising pro's/con's so the business owner can decide.  Not you.  They have to accept the risk, unless you're buying the server for them.

The current problem is a DNS issue.  Pointing them to a DNS server that is up is the best choice.  Understand that when the original DNS server is up, it should be primary, as has already been stated.

According to:
"The DNS client does not utilize each of the DNS servers listed in TCP/IP configuration for each query. By default, on startup the DNS client will attempt to utilize the server in the Preferred DNS server entry. If this server fails to respond for any reason, the DNS client will switch to the server listed in the alternate DNS server entry. The DNS client will continue to use this alternate DNS server until:

    * It fails to respond to a DNS query, or:
    * The ServerPriorityTimeLimit value is reached (15 minutes by default).  "

So -- you don't need to reboot all clients -- it will try the preferred/primary again in 15 minutes.
DrDave242Principal Support Engineer

From a business perspective, how important is Internet access for the users if the SBS server is down?  Are users complaining about the lack of Internet access because the Internet enables them to continue to conduct business in some fashion when their only Exchange/Sharepoint/etc server is inert, or are they complaining because they can't get on Facebook while the server is being repaired?

If users absolutely must have Internet access über alles, then you may add an ISP DNS server as an alternate server on the clients, but know that you may be chasing sporadic connectivity issues for as long as that configuration is in place.  If there are only one or two users who require Internet access for a legitimate business reason when the server is down, a better solution may be to show those users how to manually change their TCP/IP properties so that they can direct their machines to an ISP server when the SBS server goes down, then revert to obtaining DNS from DHCP once it comes back up...or you could write a script that does this for them if you're afraid they'll get confused - then they'd only have to remember how to kick off the script.

There's something else to think about here, though: if your SBS server is going down often enough for this to be an issue, there's something seriously wrong with that server, and your time may be best spent tracking that problem down and fixing it.
Jeffrey Kane - TechSoEasyPrincipal Consultant
Most Valuable Expert 2016
Top Expert 2014

There is a major issue with SBS 2008 and DNS failing.  You can read about it here, and apply the hotfix which should solve the problem:

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