Distributing DNS load via DHCP

[Randall C Grimshaw]

we built this logic into our scripts that produce and distribute updated dhcp configurations, thus the 'balancing' is more controlled by subnet assignment.

Randall Grimshaw rgrimsha at syr.edu
________________________________________
From: dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org [dhcp-users-bounces+rgrimsha=syr.edu at lists.isc.org] on behalf of Jeff Wieland [wieland at purdue.edu]
Sent: Friday, December 16, 2011 9:55 AM
To: Users of ISC DHCP
Subject: Distributing DNS load via DHCP

We have a fairly large pool of address, and we'd like to distribute
the DNS load on this pool between two DNS servers.

Roughly, what I was thinking of doing is:

group {
    default-lease-time 21600;
    max-lease-time 28800;
    option domain-name "myuni.edu";
    option domain-name-servers 192.168.1.5, 192.168.1.6;

    subnet 192.168.128.0 netmask 255.255.240.0 {
        authoritative;
        option routers 192.168.128.1;
        # Select the DNS server order by examining the last bit of
        # the hardware address
        if (suffix(binary-to-ascii(2, 8, ":", hardware), 1) = "1") {
            option domain-name-servers 192.168.1.6, 192.168.1.5;
        } else {
            option domain-name-servers 192.168.1.5, 192.168.1.6;
        }

        pool {
            deny dynamic bootp clients;
            range 192.168.128.11 192.168.143.254;
        }
    }
}


Or would I be better off doing something with classes/subclasses?
I'm concerned about the performance impact of the if statement.

--
          Jeff Wieland            |         Purdue University
   Network Systems Administrator  |        ITN&S Data Networks
       Voice: (765)496-8234       |        155 S. Grant Street
        FAX: (765)494-6620        |   West Lafayette, IN 47907-2115

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