mutual forwarders in ISC BIND

Damien Fleuriot ml at
Wed Dec 28 13:36:19 UTC 2011

On 12/28/11 2:07 PM, Victor Sudakov wrote:
> Damien Fleuriot wrote:
>> If you're trying to build up a cache to improve performance and response
>> time, here's your scenario:
>> DNS C, forward to DNS A,B for all queries
>> DNS D, forward to DNS B,A for all queries
>> Your cache will start building up and only responses that are not cached
>> will be taken from your NS A and B servers.
> Sorry, I fail to see how this is any better than two independent DNS
> servers. Perhaps a variant like
> DNS C, forward to DNS A 
> DNS D, forward to DNS A 
> would be close to the goal of cache consolidation.

DNS A suffers an outage ; you're fucked, to put it bluntly.

> Matthew Seaman wrote:
>> If you want to consolidate caches then probably your best bet is to have
>> fewer, but larger resolvers.  A pretty standard server class machine
>> dedicated to recursive DNS should be easily capable of supporting many
>> thousands of clients.
> You are certainly right.
>> DNS is not really a fruitful target for reducing traffic volume -- there
>> really isn't that much of it compared to all other types in any case.
>> It's also pretty critical to the perceived performance of your networks.
>>  Complicating and slowing down the DNS lookup path just makes everything
>> look slow.
> I just wanted the servers to benefit from each other's caches. That
> could speed up the lookups.

On a side note, have you considered unbound ?

It may be better suited to your needs and scale.

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