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static vs dhcp networking problem in vm

Uzamčený static vs dhcp networking problem in vm

  • Wednesday, May 19, 2010 8:46 PM
     
     
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    Hi,

    I have a Windows 2008 R2 enterprise server running as the host OS on Dell 710 poweredge server.  This server has 4 nics in it.  Nic1 is for host.  Nic2 - 4 are to be used for the vms. 

    I launch Hyper V manager, go into Virtual Network Manager.  I select external and click on add to add a virtual network.  I give it the name VM1 and select the appropriate NIC from the drop down list.  I then uncheck the allow management operating system to share this network adapter.  I click on OK.  I then select this network from the drop down list box in the VM settings.  I install the guest OS (Windows 2008 R2 enterprise).  The guest VM can surf the internet if the network card  in the guest OS is set to use DHCP.  If I use a static IP the VM loses its connection to the internet.  VM1 will be a AD and DNS server so a static IP is needed.  What am I doing wrong?

    Thanks,

    Greg

       

    All Replies

    • Wednesday, May 19, 2010 9:22 PM
       
       
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      Hi Greg,

      First of all, why do you want that your VM1 running the AD and DNS roles access to Internet ?

      A best practice Microsoft is that your Active Directory doens't have to access to Internet because
      this is the backbone of your infrastructure.

      Second of all, if you uncheck the box "allow management operating system to share this network adapter",
      you have to have an other NIC in your host for management.

      David LACHARI
         
      • Wednesday, May 19, 2010 9:26 PM
         
         
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        Greg,

        I'm thinking about something ...

        Your physical NIC is set to have a static or a DHCP address ?

        David LACHARI
           
        • Wednesday, May 19, 2010 10:18 PM
           
           
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          If a DHCP assigned IP scheme is working and a manually assigned scheme is not working...my first question is:  What is missing from the manually assigned scheme?

           

          Brian Ehlert (hopefully you have found this useful)
             
          • Thursday, May 20, 2010 12:12 AM
             
             
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            I need access to the internet to patch the server until the WSUS gets built.  It also needs network access so it can forward my DNS queries.  The problem is when the VM NIC has a static IP it can't ping anything else.  No router, no dns server, nothing.  When the VM NIC has a DHCP IP everything works fine.

            NIC 1: HOST OS: Static: 10.10.10.7 255.255.255.0 10.10.10.1

            NIC 2: GUEST OS: Static: 10.10.10.8 255.255.255.0 10.10.10.1

               
            • Thursday, May 20, 2010 12:13 AM
               
               
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              DHCP gives an IP, subnet mask, gateway, and DNS server.  I gave a static IP, subnet mask, gateweay, and a DNS server.
                 
              • Thursday, May 20, 2010 9:16 PM
                 
                 
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                OK after reinstalling the guest OS here is what I have learned.  A fresh install of 2K8 R2 with a static IP can connect to microsoft.com and download patches.  I installed the AD role and rebooted.  I can still access microsoft.com.  I run dcpromo (the NIC had the following IP information: 10.10.10.8 255.255.255.0 10.10.10.1 DNS 10.10.10.8) and let it install DNS and I can no longer access websites by name.  I can access websites by IP.  So the problem is with the DNS server that AD installed.  I checked the NIC properties and the DNS server was set to use 10.10.10.8 (the static IP of the guest OS) and found it had changed to 127.0.0.1.

                So what is wrong?  I checked the DNS server and there is no . zone (dot zone) present.

                Thanks,

                   
                • Thursday, May 20, 2010 9:48 PM
                   
                   
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                  You have to give a fail back DNS server to your DNS server.

                  Prior to Server 2008 you had to make sure to manually put a loopback DNS lookup in the DNS settins of your DNS server.  Now that setting is done for you and you have to add an external one as a secondary.

                  This is an old best practice turned into default behavior.

                  I guess none of us thought to ask about DNS resolution..

                  Brian Ehlert (hopefully you have found this useful)
                     
                  • Friday, May 21, 2010 5:35 AM
                     
                     
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                      There was a dot at the top of the DNS tree in server 2000 but not since then. I remember you had to remove it before you could enable DNS forwarding.

                     

                     

                    Bill
                       
                    • Friday, May 21, 2010 2:18 PM
                       
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                      You have to give a fail back DNS server to your DNS server.

                      Prior to Server 2008 you had to make sure to manually put a loopback DNS lookup in the DNS settins of your DNS server.  Now that setting is done for you and you have to add an external one as a secondary.

                      This is an old best practice turned into default behavior.

                      I guess none of us thought to ask about DNS resolution..

                      Brian Ehlert (hopefully you have found this useful)


                      I have a windows 2008 SP2 enterprise server running on bare metal and it is a AD and DNS server too.  I checked the NIC settings for that server and it has a static IP, subnet mask, gateway, and the DNS server is set to 127.0.0.1 and there is no secondary.  The DNS server is set to forward to my ISP DNS servers.

                      The VM server is setup the same way: static IP, subnet mask, gateway, and the DNS server is set to 127.0.0.1 and there is no secondary.  The DNS server is NOT set to forward to my ISP DNS servers.  I will try adding the forwarders and see what happens.  UPDATE: I added my ISP DNS servers as DNS forwarders and the VM can now access microsoft.com.  So as I understand this I need to have either a secondary DNS server in the IP settings or use DNS forwarders.  Windows 2008 R2 can't do direct root DNS lookups?  Somehow this doesn't make sense.

                      I didn't think about DNS resolution because I couldn't ping the default gateway.  I am thinking the original VM I created was screwed up in some way because after I deleted that VM and started over I could ping the default gateway.  I also believe the popup that says no internet access.  Maybe Microsoft should make the message more descriptive.  can't ping default gateway, no dns resolution, can't find route to microsoft.com, etc.

                      Thanks

                      • Marked As Answer by Greg_33 Friday, May 21, 2010 3:21 PM
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                      • Friday, May 21, 2010 3:17 PM
                         
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                        The situation is not that it cannot do root NDS lookups.

                        the issue is htat the alternate sources for DNS information must be configured by the administrator, it isn't just automatic.

                        The 127.0.0.1 is applied becuase ANY DNS server should look to itself (its own DNS database) first, before going and forwarding the DNS request (or proxying a DNS request).

                        Ping only measures connectivity.  That is all.  And, technically, you had connectivity - you didn't have external DNS resolution.

                        Brian Ehlert (hopefully you have found this useful)
                        • Marked As Answer by Greg_33 Friday, May 21, 2010 3:20 PM
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                        • Friday, May 21, 2010 9:49 PM
                           
                           
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                          Well I turned on VM1 this afternoon and the network icon has the yellow exclamation point in it and says no internet access.  However the server can access microsoft.com and it can ping the default gateway.

                          I am just going to leave it alone as it works.