Re: Comcast residential DNS contact

[Niels Bakker <niels=nanog () bakker net>]

* shortdudey123 () gmail com (Grant Ridder) [Wed 03 Dec 2014, 12:54 CET]:
> Both of Google’s public DNS servers return complete results every 
> time and one of the two comcast ones works fine.
>
> If this is working by design, can you provide the RFC with that info?

An ANY query will typically return only what's already in the cache.  
So if you ask for MX records first and then query the same caching 
resolver for ANY it won't return, say, any TXT records that may be 
present at the authoritative nameserver.

This could be implementation dependent, but Comcast's isn't wrong, and 
you should not rely on ANY queries returning full data.  This has been 
hashed out to tears in the past, for example when qm**l used to do 
these queries in an attempt to optimise DNS query volumes and RTT.


        -- Niels.