[ILUG] DNS resolution problem

[stephen mulcahy]

On 28/02/11 16:06, Gareth 'bigbro' Eason wrote:
> 1. You should probably not have any search stanza in the resolv.conf on
> a server. Search is useful for a desktop machine as (lazy) humans want
> to use it and not bother typing in a fully qualified domain name. For
> servers you should be specifically configuring FQDNs to optimise
> traffic. (Of course, now someone will provide an equally compelling
> reason for using search on a server ;)  )

There is certainly an argument for what you propose. Note that you'll 
also need to remove the domain directive from your resolv.conf if this 
is your chosen approach to "fixing" the problem. And you'll still 
generate two queries instead of one for most addresses.

> 2. Seriously, the correct fix is to get those domain holders to enable
> IPv6 and provide AAAA records for their domains. Changing the order of
> lookups changes the preference for IPv6/4 in contravention to the RFC,
> and common sense. Surely if a better / later version of something is
> available you want to prefer that?!? In particular, I fully expect that
> in a few years you'll see the opposite happening as many hosts don't
> have an A record at all and your DNS will spuriously attempt to find it
> before trying IPv6.

Your argument echoes a lot of the comments on 
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=268631

It sounds like a discussion for the pub to be honest. For me, contacting 
a few million domain holders to explain the problem and request them to 
provide AAAA records for their domains sounds like a significant piece 
of work. While you're right that the situation will change in a few 
years, so will the version of the Linux distribution that I'm running. 
Personally, I think the pragmatic solution for the next year or two 
would be to default to IPv4 lookups before IPv6 and review the situation 
in a year or two.

The bottom-line here is that there must be lots of servers out there 
generating lots of unnecessary DNS queries atm.

For now, I'll go down the road of tweaking my /etc/gai.conf - anyone 
with a working config giving precedence to IPv4 lookups? My initial 
experiments have been unsuccessful.

-stephen

-- 
Stephen Mulcahy     Atlantic Linux         http://www.atlanticlinux.ie
Registered in Ireland, no. 376591 (144 Ros Caoin, Roscam, Galway)