Algorithm 'When to use EDNS0'?

[Mark Andrews]

In message <1322689151.15146.69.camel at mjelap.posix.co.za>, Mark Elkins writes:
> On Tue, 2011-11-29 at 15:36 +0200, Mark Elkins wrote:
> > When does 'EDNS' get brought into the picture?
> > A 'dig' with '+dnssec' works just fine (more than 512 bytes over udp) -
> > but a dig without '+dnssec' and actually asking for the 'dnskey' records
> > for a domain - which is over 512 bytes - does a "Truncated, retrying in
> > TCP Mode" on me - even when asking "localhost".
> 
> Thanks for the private replies...
> 
> All this comes about as I had the expectation that DIG would run in a
> similar way to any other 'dns lookup' - which it currently doesn't.
> Neither does it have any form of config file.

Actually dig does have a config file.

       It is possible to set per-user defaults for dig via ${HOME}/.digrc.
       This file is read and any options in it are applied before the
       command line arguments.

> So adding '+dnssec'
> obviously adds the '+edns=0' switch. I'm told that in a future software
> release that '+edns=0' will be default behaviour - that sounds like a
> reasonable thing to do.
> -- 
>   .  .     ___. .__      Posix Systems - (South) Africa
>  /| /|       / /__       mje at posix.co.za  -  Mark J Elkins, Cisco CCIE
> / |/ |ARK \_/ /__ LKINS  Tel: +27 12 807 0590  Cell: +27 82 601 0496
-- 
Mark Andrews, ISC
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PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org