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lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

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  • lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

    Hello,

    I've always known enough to be dangerous wrenching on our small businesses servers for 14+ years...but no formal MS education.

    We have a two year install of SBS2008 doing just fine with a 2003 Server R2 being a 2nd DC/DNS server.

    We lost the SBS2008 server for about 6 hours today...for some reason it simple quit recognizing the NICs and although I"m not really sure what failed or even how I fix it, it's back up.

    My primary concern is all computes on our network went brain dead. Nothing could talk to nothing although a local ipconfig showed they still had their dynamic IP address from DHCP still prior to the DHCP failure.

    I always understood in the event of a failure the 2nd DC/DNS should have forfilled all requests so everyone could continue to work. I did some NSLOOKUP and can see the 2nd server is there.

    Questions:

    1. Should the 2nd DC/DNS being fullfilling requests when the SBS2008 goes offline?
    2. Where should I start to understand what has failed here...do I need re-educated?

    Any useful advice to make sure I'm understanding how the system should work and where I may have failed with setting up a backup system to handle requests.

    Thanks.
    Shawn

  • #2
    Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

    What kind of "requests" are you referring to? Do you mean DNS queries, AD logons, etc. or are you referring to access to things like file shares and Exchange?

    Comment


    • #3
      Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

      Are the clients configured to use both DNS servers?
      (Post an IPCONFIG/ALL from one)
      Tom Jones
      MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
      PhD, MSc, FIAP, MIITT
      IT Trainer / Consultant
      Ossian Ltd
      Scotland

      ** Remember to give credit where credit is due and leave reputation points where appropriate **

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      • #4
        Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

        By requests I mean the simplest of things...a ping even!

        When the SBS server went down not one of our 30 clients could talk to anything on the LAN or Internet, a simple PING cmd from those clients failed. If I did a local ipconfig you could see the client was still holding it's DHCP value so I just assumed all internal and external DNS was failing. So by requests I mean everything...

        If you look at the attached screenshot you'll see that 10.0.0.2 is my SBS server and thus DHCP and DNS while 10.0.0.3 is the "other" DC/DNS server.

        Am I not understanding a basic principle(s) of what a 2nd DC/DNS server should be doing or do I have a bigger issue at work!
        Attached Files

        Comment


        • #5
          Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

          Were you pinging by name or ip address? If you were pinging by ip address then you have a different issue because DC and DNS services aren't relevant to pinging by ip address.

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          • #6
            Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

            That is a great question/observation and regrettably I'm not 100% sure...I'd like to think I did the right thing and tested both ways but my mind was racing to fast with worst case scenarios...I cannot answer that in confidence.

            If I had to guess I feel I most likely pinged by IP address too as well as name, so if that is the case I probably need to consider the switch that services those servers, clients and the firewall...that switch would take down everything that was testing and produce the symptoms I saw.

            I'll shut down the SBS server tonight after hours and see if I can replicate anything to move this discussion forward...otherwise I'll bet I need to take a better look at that switch.

            Comment


            • #7
              Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

              That's a good idea. Try these during your test:

              nslookup

              ping by name

              ping by ip address

              ping default gateway

              log off and on from a client machine and run "Echo %logonserver%" from a command prompt

              run "\\domain.tld" from the Run command and verify connectivity to the SYSVOL share

              run gpupdate/force from a command prompt

              Post the results/messages from these tests back here

              Comment


              • #8
                Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                I'll run those tests...but I do have another question about DHCP that has me perplexed against what I thought I knew...

                1. I took down the SBS server while watching pings to clients and the intertube
                2. As expected all clients (static or dynamic) retained their IP address and could ping one another and surf the net
                3. I then restarted one client while the SBS was offline (thus DHCP is offline)
                4. That client didn't find the network again, it was now off the network...it didn't retain it's last know IP.
                5. I went to that client and IPCONFIG showed that it had no IP from our domain, it was officially off the network until the SBS/DHCP was brought backup.

                I thought DHCP clients still retained their IP even after a reboot if the DHCP is down?
                So anytime the DHCP server is offline and a client reboots it gets nothing and thus that client is now off the network from other resources?
                Is there a setting to change this bahavior or is the only answer static for all clients then?


                Will run all those tested shared with me to confirm alt DC/DNS server is working while primary is offline

                Comment


                • #9
                  Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                  When a DHCP client reboots it issues a DHCPRequest to the DHCP server to ask permission to continue using it's leased ip address. If the DHCP client doesn't get a response it then pings the DG. If it receives a reply to the ping it continues to use it's leased ip address. If the ping to the DG fails it releases it's ip address.

                  Do you allow pings to the DG? If not, that would explain the behavior. If you do, then there's a registry edit you can set to not ping the DG to over-ride this behavior.

                  Comment


                  • #10
                    Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                    I don't know what a DG is...but I"m guessing this is "domain x" which means the alternate domain server?

                    If that is true I can ping it just fine...I permit ping on all systems.

                    Any idea what that reg edit is so I can test it out? I'll do some searching tonight...but now I'm trying to figure out why our exchange emails cannot get out to the internet while we can receive them just fine! New poste needed!

                    Comment


                    • #11
                      Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                      DG = Default Gateway.

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                      • #12
                        Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                        Yes, the DG is "ping'able".

                        Why does it do this...is it looking for an IP from the internet/gateway as a backup plan?

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                        • #13
                          Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                          It's checking to make sure that it's still connected to the same network as when it got it's ip address lease. It does that by pinging the DG that was assigned as part of the DHCP ip address lease.

                          If the DG responds it assumes that it's still connected to the same network, if the DG doesn't respond it assumes that it's been moved to another network.

                          Admittedly, this doesn't seem like the most sophisticated design, but it is what it is.

                          You do assign the DG as part of the DHCP ip address lease, right? I can't see any other way of doing it.
                          Last edited by joeqwerty; 10th October 2012, 00:35.

                          Comment


                          • #14
                            Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                            got it.

                            So once I figure out the registry setting I'd have to write a GP to solve this need on all clients...or is the registry hack just for the DHCP server?

                            Comment


                            • #15
                              Re: lost SBS 2008 NIC and "alt" DC/DNS didn't help fulfill requests, very confused!

                              The registry setting is for DHCP clients. Here's an article releveant to Windows Vista, but is probably valid for XP as well:

                              http://support.microsoft.com/kb/958336

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