How do I use a load balancer with my name servers?

Answered Fri, 25 Oct 2002

> Just wanted to ask a question about load balanced DNS servers
> via an external network load balancing appliance (i.e - F5's Big IP,
> Cisco's Content Switches/ Local Directors).
> The main question being the configuration whether to use 2
> Master/Primary Servers or is it wiser to use 1 Primary and 1
> Secondary? The reason is that I feel there are two configurations
> that could be setup. One in which only the resolvers query the
> virtual IP address on the load balancing appliance or actually
> configure your NS records to point to the Virtual Address so that all
> queries, ie - both by local queries directly from local users and
> also queries from external DNS servers. I've included a text
> representation of the physical configuration. Have you ever
> heard or architected such a configuration?
>
>      VIP = 167.147.1.5
> ------------------------------------
>> Load Balancer Device |
> ------------------------------------
>                 |
>                 |
>           -----------------
>            |           |
>  ----------------         --------------
>> DNS 1     |         | DNS 2   |
>  ----------------         --------------
> 1.1.1.1               1.1.1.2

There's usually not much need to design solutions like these, since most
name server implementations will automatically choose the name server
that responds most quickly. In other words, if DNS 1 fails, remote
name servers will automatically try DNS 2, and vice versa.

However, it can be useful for resolvers. In that case, you don't need to
worry about NS records (since resolvers don't use them), just setting up
a virtual IP address.

> Also, Is there any problems in running two Master/Primaries?

Just that you'd have to synchronize the zone data between the two
manually.

cricket