[NTLUG:Discuss] Use DNS for redundant geographic sites?

[Neil Aggarwal]

Hello:

I am trying to figure out a way to create a web site
that is multi-homed geographically.

I just thought of this idea:

I will have two machines, each located in
a different place.

Machine A will run:
	dnsA.jammconsulting.com (DNS server)
	webA.jammconsulting.com (Web Server)

Machine B will run:
	dnsB.jammconsulting.com (DNS server)
	webB.jammconsulting.com (Web Server)

Now, lets assume that I register a new domain
name.  For discussion, lets use jammconsulting.com
as the domain name.

In the domain records, I set the DNS servers to
be:
	dnsA.jammconsulting.com
	dnsB.jammconsulting.com

Now, here is the strange part:

dnsA will always resolve www.jammconsultng.com to 
the IP address of webA and dnsB will always resolve
www.jammconsulting.com to the IP address of webB.

This way, if either machine goes down, the machine
will not respond to DNS queries.  The DNS will query
the other machine and all traffic will go to it.

I know this does not protect me against the situation
where dnsA is up and webA is down, but as long as
the machine is up, I can set up monitoring of the
web server.  Usually, Apache httpd runs without a
problem.

Will DNS clients handle a situation where the 
nameservers give different responses?

Are there other downsides I have not considered?

Thanks,
	Neil

--
Neil Aggarwal, (214)986-3533, www.JAMMConsulting.com
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