dns server redundancy

[Kevin Darcy]

Kris wrote:

>What's the best way to have dns server redundancy?  In my case, we have
>issues with running out of recursive queries (we've jacked that limit up to
>10000).  From what I've read, it seems my best bet is to add more
>nameservers to the mix.  If I set up the zone information for the nameserver
>as so:
> 
>
>nameserver        600       IN         A          10.0.0.3
>
>nameserver        600       IN         A          10.0.0.4
>
>nameserver        600       IN         A          10.0.0.5
>
> 
>
>does this mean that requests for nameserver will be divided equally among
>the 3 servers listed?  Will this, then, help alleviate the issue we're
>having with server failure due to excessive recursive lookups?
>
No, the address that a name resolves to has nothing logically  to do 
with what nameserver you ask to resolve it. If you want to spread out 
the load from a bunch of recursive clients the most straightforward way 
to do so is by changing the resolver configurations on those clients. 
This isn't so hard if you're using DHCP; in fact, some DHCP products 
have a "rotate" option which automatically gives out different 
permutations of a given resolver list to different DHCP clients, 
specifically for the purpose of spreading out query load.

Another option, I suppose, is to put load-balancer(s) of some sort 
between your nameservers and their clients...

                                                                         
                                                         - Kevin