Redundancy for recursive resolvers w/dual ISPs

Pete Ehlke pde at
Mon Jan 13 19:12:46 UTC 2003

On Mon, Jan 13, 2003 at 10:49:55AM -0800, Chris Timmons wrote:
> My question is, should I consider a scheme which would allow the name
> servers from both networks to share a site-wide cache?  I thought of a
> way to do this by configuring two new site-wide recursive name
> servers, one from each network - and then configuring each existing
> name server to forward to the pair.  The good news would be the
> site-wide cache and potentially the small benefit (stop applications
> from hanging on DNS and let them get right to the absence of L3
> connectivity :) if 1 of the 2 ISPs goes down.  Unfortunately such a
> configuration seems inefficient and overly complex.  Should I bother?
> Any magic bind9 features to let the caches corrupt each other without
> all of that forwarding?
There is significant recent work showing that caches reach 80% or more
of their potential richness very quickly with as few as 20 clients
pointing at them. The benefits you may see from configuring a large
central cache are likely to be extremely small, and IMNSHO are vastly
overshadowed by the added complexity.


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