dns based loadbalancing/failover

[bert hubert <ahu () ds9a nl>]

On Sat, Oct 06, 2001 at 01:31:47AM +0200, Peter van Dijk wrote:

> - the box, continually monitoring rtt's and reachability of networks,
>   returns the A record pointing to the most 'optimal' ISP for that
>   client. This request then comes in, it NATs it to the RFC1918 space
>   and handles it.

The really neat thing is that you can do this with any nameserver. Install
N nameservers and connect each of them to one of your ISPs. These
nameservers are all masters, and all contain different data. 

Each one responds with data relevant for the IP addresses of that ISP. If
all your links are up, people will get mixed responses. If one ISP is down,
that nameserver will stop answering, and hence after your TTL expires, no
requests will be made for those IP addresses.

It gets even better - recursing nameservers have the habit of locking in to
nameservers that respond quickest. So you even get some loadbalancing
awareness.

We operate nameservers in the US and in Europe, and we definitely see this
effect.

Regards,

bert

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