DNS load balancing with CNAME possible?

[David Botham]

bind-users-bounce at isc.org wrote on 04/16/2005 01:18:24 PM:
> Hi all.
> 
> 
> I have 2 dsl connections with dynamic ip addresses which have ports 25
> and 110 forwarded to the same host. I want to balance the load between
> the two dsl Internet connections by doing this:
> 
> pop.mydomain.com.   300   IN   CNAME   dsl1.gotdns.com.
>                           IN   CNAME   dsl2.gotdns.com.


These entries will not work.  What is on the left side of a CNAME RR 
cannot be on the left side of any other RR's in the name space.  In your 
example, the second RR would constitute a second RR with the same left 
side.

> 
> 
> But, the gotdns.com domain is not managed or hosted by me. What it is
> is a free service (by dynip.org) where I have registered and that will
> update the ip address of either of the dsl connections in case my ISP
> changes it.
> 
> Is it possible to do this?  I tried and my dns will only resolve for
> pop.mydomain.com with the last CNAME in the list. Is there any way to
> do this and if so what am I doing wrong?  When I use ip addresses (A
> type records) it works very nice.

Two A RR's would be your only choice.

All of that being said, round robin DNS is probably not going to be an 
effective way to perform load balancing of inbound traffic on different 
links.  You may want to look into an appliance that is designed for this 
purpose.  F5 Link Controller and Radware LinkProof are two devices that 
come to mind quickly.  I am sure there are others. 


> 
> Finally, my named server is running on a Linux host and while I
> haven't yet figured out how to know the bind version, the man pages
> displays "4th Berkeley Distribution"

Try this at the command prompt:

dig chaos txt version.bind @127.0.0.1


hth,


Dave...


> 
> Any help will be appreciated.
> 
>