[AusNOG] Speaking of DNS...

[Geordie Guy]

It is indeed a simple and useful tool but it only gives a 10000 ft overview
of what's going on.  Tools like that get a collection of servers (or
routers with IP dns-server command run on them for the coterie of NOGgers
who insist that any post that doesn't include three AS numbers and a
traceroute is off topic and layers five through seven of the OSI Reference
Model are some sort of New Testament heresy), one per country or continent,
and shows you what IP they resolve for a given fqdn.  As network operators
we know that's a fairly blunt instrument.  Yesterday's drama for us showed
that the primary problem we had in the wake of the whoopsie was that
Telstra's DNS infrastructure for enterprise and business seems to have a
shorter TTL or caching lifetimes on those IP records than the Bigpond side
of their business does, that smaller partners and customers of ours might
use.  This allowed us to figure out where it was working and where it
wasn't, but as far as WhatsmyDNS was concerned all of Australia
(represented by a single DNS server) was ok.

So yeah, if you're the type of wag who unveils a new business service by
changing a DNS record, whatsmyDNS will give you an idea of the geographies
that you can probably expect your service to be live in and who is still
getting the coming soon page with the animated gifs of the construction
signs, but if you've got a local problem with different Australian networks
having different results then you need looking glasses or a community of
operators who can give you their view of the world.



On Thu, Feb 13, 2014 at 10:38 AM, Nathan Phelan
<nathan at interconnekt.com.au>wrote:

> Nice one Mark!
>
> https://www.whatsmydns.net/ is a simple dns tool too.
>
> Cheers,
> Nathan
>
> -----Original Message-----
> From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Nishal
> Goburdhan
> Sent: Wednesday, 12 February 2014 8:45 PM
> To: Mark Foster
> Cc: ausnog at lists.ausnog.net
> Subject: Re: [AusNOG] Speaking of DNS...
>
>
> On 12 Feb 2014, at 9:23 AM, Mark Foster <blakjak at blakjak.net> wrote:
>
> > ... what's the done method of troubleshooting DNS problems that only
> affect certain network(s), now that open resolvers are (hopefully) a thing
> of the past?
> > I have semi-regularly struggled with troubleshooting email delivery
> problems (for example), due to an inability to see what ISP X sees as my MX
> record.
> >
> > Onceuponatime I could just query their DNS servers myself. Now it seems
> I either have to hope that their helpdesk understand what an MX record
> actually is, or try to find a shell account on a machine within their
> network to tinker with...
> >
> > I didn't realise that DNS was something that was a candidate for a
> network of 'looking-glass' systems, but perhaps it is... Need a nice,
> rate-limited, hard-to-abuse web-based DNS lookup tool to become commonly
> available, perhaps?
>
>
> http://www.bortzmeyer.org/dns-lg.html
>
>
> --n.
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