We have 2 servers, I'll call them NS1 and NS2.

NS1 is our primary web/email/name server.

My goal is to set up NS2 as a hot backup web/email/name server.

I understand the correct MX entries for NS2, I just give them a lower priority than NS1 and everything should be properly recieved on NS2 and forwarded to NS1 in the event that NS1 is down for a bit.

What I don't understand is how to set up the correct A records on NS2, so that web traffic is pointed to NS1 if it's up and running, and to NS2 if NS1 is down. Or maybe I don't use A records on NS2?

Can anyone help?

Hi driverdave,

What you are trying to do is have the DNS server "intelligently" route all web traffic to the 1st server, unless it is down, then it should route to the 2nd server.

This is usually called DNS-based load balancing.
There are various methods of doing this.

For a complete, complex solution, try http://www.stanford.edu/~schemers/docs/lbnamed/lbnamed.html

But that is a bit complicated to setup and needs some customization.

Alternatively, you can use the multiple-A records method:
Put an A record for each of your webv servers on both DNS servers.
e.g.:
www.bla.com. IN A 1.2.3.4
www.bla.com. IN A 2.2.2.2

Regards,
Matt
WhiteCollar / WhiteCollar18

Set up your NS2 DNS server to be a backup DNS or secondary DNS server. Do so by configuring the zone file to act as a secondary DNS server for the given host name. Once you reload the process for that domain, it will automatically pick up the configuration from the primary DNS server.

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