a beginner's questions on failover using DNS

[Simon Waters]

Rosie lee wrote:
> 
> I've just started investigating in this field and tried to find
> solutions for failover/load balacing using DNS (I also looked up some
> router solutions like those from Cisco which are far too expensive
> for SMEs).
> 
> I checked the archives and found something related but quite a while
> ago. Hope somebody give  me any most recent information.
The usual response is "don't use DNS for load balancing"/"fail over".

> In my case, a X company just got a broadband connection with much
> greater bandwith than the previous ADSL lines. And they want to use
> this as the primary network connection and keep the ADSL as backup
> options. Failover is the major concern here. So when the primary
> connection down, the ADSL can be used upon users' requests. I am not
> sure how Round Robin works when one of the servers fails (I am
> wondering if Round Robin just send a user an IP address on the top of
> the list no matter the host is down or not). Can RRset ordering
> option give a better solution currently? Are there any alternatives
> (like Microsoft DNS server) doing a better job than BIND?

What are you actually trying to achieve?

Outgoing traffic is readily handled by routing, DNS doesn't have to get
involved. Since the name and IP of the destination are unaffected by the
workings of one of your network links.

Incoming mail can easily be handled by putting two MX records for the
host one via each link, the priority being for the faster link presumably?!

So what sort of services are you offering to the outside world that
needs fail-over support on these links?


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