[aklug] Re: Bind/DNS TTL override

From: <bryanm@acsalaska.net>
Date: Sat May 21 2011 - 17:40:35 AKDT

On Sat, May 21, 2011 2:35 am, Scott A. Johnson wrote:
> I'm running a local recursive Bind server on my LAN to help speed up
> repetitive DNS lookups due to a high latency satellite connection. The
> thought process being for every DNS record I can look up locally from a
> previously cached copy, that shaves 600ms+ off my load times. The problem
> is that so many sites these days use really low TTL in their DNS records for
> load balancing, almost making the local DNS server useless. The fact I may
> have unintended consequences by overriding their TTL notwithstanding, can I
> somehow override the TTL given to Bind for domains/zones to a higher value?
> I've done some Google searches but can't find too many/any people looking
> to do the same thing. I'm not married to Bind either, so if I can do this
> through another caching/recursive DNS daemon I'm fine with that too.

Dnsmasq (http://www.thekelleys.org.uk/dnsmasq/doc.html) mentions
this option in its man page:

--max-ttl=<time>
    Set a maximum TTL value that will be handed out to clients. The specified
 maximum TTL will be given to clients instead of the true TTL value if it is
 lower. The true TTL value is however kept in the cache to avoid flooding the
 upstream DNS servers.

I haven't used that option, but maybe it's the kind of thing you're
looking for.

--
Bryan Medsker
bryanm@acsalaska.net
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Received on Sat May 21 17:40:42 2011

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