BIND9, DynDNS, Multiple RRs

[Chris Buxton]

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On Sep 23, 2008, at 1:07 PM, Alan Clegg wrote:

> Theophanis Kontogiannis wrote:
>> However É do not see a way to do CNAME based load balancing for www.abc.biz
>
> Why use cnames?  Why not:
>
> www.abc.biz	IN	A	ip.ad.dr.1
> 		IN	A	ip.ad.dr.2


That's not the whole answer, though, because the records would need to  
be dynamically updated when one or the other IP address changes. Some  
kind of custom script is required that somehow monitors those  
addresses and changes them as needed (including removing stale  
addresses). It might be best to create a subzone (www.abc.biz) that's  
dynamic, allowing the rest of the abc.biz domain to be static.

Maybe a cron job that runs a script like this:

#!/bin/bash
IP1=$(dig @ns.dyndns.biz a.dyndns.biz +short)
IP2=$(dig @ns.dyndns.biz b.dyndns.biz +short)
# do something to validate that real IP's were returned, then...
cat << EOF | nsupdate -k key.file
server a.dyndns.biz
update delete www.abc.biz
update add www.abc.biz 60 A $IP1
update add www.abc.biz 60 A $IP2
send
EOF

(Note: Untested, may contain syntax errors, and it's missing a  
function to validate the IP's.)

Chris Buxton
Professional Services
Men & Mice

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