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Site Link Design question

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  • Site Link Design question

    Iíve posted here a few times and had some great advice. Iím moving right along with my project but had a question about site link design. A little background.

    Iím designing a large migration from NT 4.0 to WIN 2003 AD. It is a branch office scenario or hub and spoke. There will be 2 identical datacenters (hubs) and about 50 branch offices. Each datacenter will have 2 DCís and each branch will have 1 DC. All DCís will be GCís and the network is fully routable.

    My plan was create site links between the datacenter and braches and evenly distribute them. Because there are 50 branches, I would have 25 braches with site links to one datacenter and 25 with site links to the other datacenter. One datacenter is in Nashville and the other is in Chicago so some example links would be Charleston/Chicago or Cincinnati/Nashville. Then I thought, does it make sense to have both datacenter sites in each site link as in Charleston/Chicago/Nashville? The Chicago and Nashville datacenters will replicate with each other as quickly as possible so Iím not sure if this is a good idea.

    The other idea was create a second site link for each branch that talks to the other datacenter with a higher cost. For example create Charleston/Chicago site link with a cost of 200 and also create Charleston/Nashville with a cost of 400. So the Chicago datacenter is the priority. I do realize that cost refers to the most efficient site link or higher WAN speeds equals lower costs. All branch offices will have the same WAN link speed from either datacenter, so again Iím not sure if this makes sense?? My thinking is that Iím adding some redundancy.

    Any comments are greatly appreciated-


  • #2
    Re: Site Link Design question

    First of all, please check if each office should have unique site.
    Also, you can create two sites link, and but checking the free connection bandwidth you can define what site link will get prefer on the other.
    In most of times, there no need to create manually site connection due the nature of KCC (Dont forget to set each DC as DNS server also)


    Best Regards,

    Yuval Sinay

    LinkedIn:, Blog:


    • #3
      Re: Site Link Design question

      If you stick to defaults and keep site link bridging enabled, there is no need for the second link - if the hub, to which the branch office is "linked", is down, the branch DC will still be able to replicate with other DCs. The downside is that in this setup you have no control over which DC it will pick (it could be any branch or hub DC in the domain).

      So the question is: are you planning to disable site link bridging ? If you do, having a higher cost link to second hub would probably be a good idea, otherwise (if you do not mind uncontrolled replication topology during hub site failure) you can get away with single link per branch site.
      Guy Teverovsky
      "Smith & Wesson - the original point and click interface"


      • #4
        Re: Site Link Design question

        Thanks for the info. I think I'm going to keep site link bridging enabled and let AD choose backup replication partners for failover. I was considering manual site link bridges so that the branch DC's will only replicate with the DC"s in the Chicago or Nashville Hubs. But both Hubs will have 2 DC's and the chance of them both failing at the same time isn't very likely. If it does happen and the branch DC's contact another branch DC, so be it.

        Thanks again! This site has been extremely helpful to me.