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DNS Algebra

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  • DNS Algebra

    OK, this is a very basic question, but I haven't found an answer after Googling various search terms.

    Is there a formula for the number of DNS servers you should have according to the number of client machines? My boss is wanting to segment DNS on the network, which I think is unnecessary. For one, instead of being able to assign primary and secondary DNS servers in DHCP, if we segment the network, I'll have to do so at the scope level, instead of at the server level. That's a lot of scopes.

    I can find no best practices regarding this. We have about 15,000 machines on the network, with Metro-Ethernet connecting every site, and it is my opinion that a DNS request uses very little resources, I don't see how separating the network and dividing those computers among 6 DNS servers is going to make that big a difference. I mean, our Internet connection has never slowed because of a backlog of DNS requests.


  • #2
    Re: DNS Algebra

    Only "arithmetic" I have ever seen (or used) is that a local DNS server (per site) is better than a remote one, and that two (per site) is better to allow for down time
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    IT Trainer / Consultant
    Ossian Ltd

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    • #3
      Re: DNS Algebra

      We have 2 per physical site in our organisation.

      This allows us to have redindancy in the event that one fails.

      Typically i would have DNS installed on a DC.


      • #4
        Re: DNS Algebra

        Well, we have 5 DCs, all running DNS, but only specify 2 of them for all PCs in the district (usually the ones without important FSMO roles). All domain controllers reside in our central office, which is where all Internet traffic is routed anyway; none of our schools have a WAN router. The primary DNS server is physical, the secondary, virtual. With 60+ satellite locations throughout the city, it is not feasible to host a server at each site. I mean, that's the way we used to do it, but we decided it was better to spend money on Metro-Ethernet between sites than maintain 60+ extra servers (you've never seen replication hell until you've witnessed it through that many domain controllers).

        Basically, do y'all think we'd gain any benefit from separating the schools into zones and hosting a server in each zone? All schools are on separate virtual networks now.


        • #5
          Re: DNS Algebra

          If your links between offices are quick enough then i don't forsee any problems using the main head office site for DNS.