Date: Mon, 15 Jan 2001 06:06:38 -0600 From: Bob Martin <bob@buckhorn.net> To: freebsd-isp@FreeBSD.ORG Subject: Re: DNS redundancy & load balancing Message-ID: <3A62E7CE.973C0A97@buckhorn.net> References: <NEBBJFIIGKGLPEBIJACLKEJDCMAA.davew@sai.co.za>
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Dave Wilson wrote:
>
> Hi guys, howzit going ?
>
> We have a primary & secondary DNS server on our local network.
> We need some utility or setup that will automatically allow our secondary
> DNS to totally take over from our primary DNS in the event our primary DNS
> goes down.
>
> This means effectively that that in the event of a primary DNS failure our
> secondary DNS must be able to change it's own IP address to that of the dead
> primary DNS server and take over all resolution etc.
>
> I know little about load balancing or clustering so any input would be
> appreciated.
> Thanks.
>
> Kindest regards
> David Wilson
> The S.A Internet
>
> #include <std-disclaimer.h>
>
Cisco routers with IP plus can do this for you with NAT/load balancing.
Both servers get a "bogus" address NAT'ed to both real IP's. Also, most
modern programmable switches can also do this to some degree. See the
appropriate documentation for details.
You could also write a perl script to check for the presence of a box,
and if it's not available, assume it's identity. But that can be very
messy when the second box comes back on line.
If you have a lot of traffic, you might want to look at a hardware load
balancer.
And finally, if the clients are connecting to you via a NAS, check the
docs on the NAS to see if/what it can do for DNS. We are using Total
Control 1000's, and they assign themselves as the DNS server, and handle
all DNS queries in forward only mode. Completely solves the problem.
A foot note. The resolver routines in 98se and new MS products work
fine. But both MS and Netscape added DNS "helpers" to their browsers
that cache DNS server addresses. We never had problems with a DNS server
going off line until they did this.
Bob Martin
--
As far as the laws of mathematics refer to reality, they are not
certain, and as far as they are certain, they do not refer to reality.
-- Albert Einstein
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