Server 2008 failover cluster...force change of IP on failover

Discussion in 'Clustering' started by Jeff Strubberg, Jul 29, 2009.

  1. We have two 2008 server boxes with Hyper V loaded and virtual servers running
    happily. We use a product called GeoCluster to replicate from on elocal disk
    to another, allowing us to separate the two servers from a shared disk
    resource.

    With this configuration,we can run a cluster that is geographically
    dispersed and has nodes in seperate subnets on our WAN. Where we run into a
    problem is that virtual machines in the cluster do not change IP addresses
    when they migrate from one host to another.

    Writing a script to change the IP address and gateway address is fairly
    trivial. Where I am stuck is how to trigger that script? Does 2008 failover
    provide any way to call a routine only when failover occurs?
     
    Jeff Strubberg, Jul 29, 2009
    #1
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  2. You could add a generic script resource to your Hyper-V Application Group.
    This resource would be triggered any time the resource comes online.

    Regards,
    John

    Visit my blog: http://msmvps.com/blogs/jtoner
     
    John Toner [MVP], Jul 29, 2009
    #2
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  3. Dave;
    Not sure our applications would allow a roaming address. Also, wouldn't
    that leave you waiting on a dns update after a failover before clients could
    reconnect?
     
    Jeff Strubberg, Jul 30, 2009
    #3
  4. John,

    That resource would move with the machine, correct? Meaning it would assign
    the wrong IP address half the time. I'm not sure that's a big problem, since
    IT personnel would likely be present for the move back to primary hardware.
     
    Jeff Strubberg, Jul 30, 2009
    #4
  5. The more I think about it, the better this solution seems. Are MAC addresses
    in 2008 virtual machiens stable, or are they dynamically assigned? If I had
    a stable MAC, I could set a reservation in each of the two cisco switches
    involved, then leave the virtual machine in DHCP mode.
     
    Jeff Strubberg, Jul 30, 2009
    #5
  6. Yes, and this is true for almost every multi-site type of failover. Clients
    need to get the new IP and start using it, which requires low TTLs on the
    host records.

    --
    Russ Kaufmann,
    MVP, MCSE: Messaging and Security, MCT, MCITP, MCTS and other stuff

    ClusterHelp.com, a Microsoft Certified Gold Partner
    Web http://www.clusterhelp.com
    Blog http://msmvps.com/clusterhelp
     
    Russ Kaufmann, Jul 31, 2009
    #6
  7. MAC addresses are based on the MAC address of the physical NIC being used.


    --
    Russ Kaufmann,
    MVP, MCSE: Messaging and Security, MCT, MCITP, MCTS and other stuff

    ClusterHelp.com, a Microsoft Certified Gold Partner
    Web http://www.clusterhelp.com
    Blog http://msmvps.com/clusterhelp
     
    Russ Kaufmann, Jul 31, 2009
    #7
  8. Augh... Back to your question...

    If you use DHCP with reservations in each location, then the MAC address of
    the VM will indeed be stable and can be used in each location.

    --
    Russ Kaufmann,
    MVP, MCSE: Messaging and Security, MCT, MCITP, MCTS and other stuff

    ClusterHelp.com, a Microsoft Certified Gold Partner
    Web http://www.clusterhelp.com
    Blog http://msmvps.com/clusterhelp
     
    Russ Kaufmann, Jul 31, 2009
    #8
  9. I agree, a virtual machine that could handle geographic dispersion over a
    layer 3 network would be quite an enhancement. As for clients picking up the
    new IP, this box runs a single app. I can change the client side icons to
    call a dns refresh, then the application. That should cut changeover down to
    just how long it takes for the virtual machine to report the IP change.

    Thanks Dave, Russ. This looks like a much better solution than me trying to
    graft a layer two link between two layer three sites.
     
    Jeff Strubberg, Jul 31, 2009
    #9
  10. Yes, the resource would move with the machine. You would need to develop the
    script so that it checks the owning node and then assigns the proper
    address.

    Regards,
    John

    Visit my blog: http://msmvps.com/blogs/jtoner
     
    John Toner [MVP], Jul 31, 2009
    #10
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