Re: [PLUG] home dns notes

[aab@drexel.edu]

Set up a cron job to poll your external DNS server and pull either the
records and cache them (compare the new pull vs. the cached info) *OR*
pull just the serial number ... if it doesn't change, you can assume a
change hasn't taken place at the external host.

Set your internal DNS such that your serial number is *slightly* newer
than the external ... pull both serial numbers and compare.  If you're
seeing an external newer than the your internal server, have it send a 
message to you to manually update your home DNS.  The advantage here's
that you are still maintaining control of the home DNS info vs. having
some external entity effectively inserting records in your home DNS.

Should be relatively easy to pull off.

andrew.

On Wed, 8 Aug 2001, Jeff Abrahamson wrote:

> Those of you paying as much attention to my problems as I do may
> recall my saying the below quoted text a few days ago.
> 
> I thought I'd provide a brief follow-up on why it all fell apart...
> 
> It turns out that sendmail really does care a lot about dns
> lookups. (Yes, I could have recompiled sendmail with dns off.) Well,
> so /etc/hosts wasn't good enough for sendmail, it wanted real dns.
> 
> So I caved in and did the internal/external dns thing. Works fine. You
> all get to see purple.com external dns. I have an internal version
> that resolves local hosts but that also has to know about the external
> ones.
> 
> The only drawback is that there's no automatic update of the internal
> when an external host IP changes. Fortunately, my empire is small and
> this is not a big worry.
> 
> -Jeff
> 
> 
> On Sun, 5 Aug 2001, Jeff Abrahamson wrote:
> > The problem is that if I claim authority over purple.com, I can't see
> > the outside purple things (www, list). If I claim authority over a
> > subdomain, I don't get there, since the lookups are com -->
> > purple.com, which doesn't know about home.purple.com subdomain.
> > 
> > So the solution was to use /etc/hosts to declare all my local
> > names. My nsswitch.conf of course says "files dns". Then I declare dns
> > authority over 0.168.192.in-addr.arpa to get reverse resolution
> > working (important for ssh, sshd, and the like--avoiding dns timeouts
> > on my lan). And now it appears that all works fine (if I don't poke
> > too much with nslookup / dig).
> 
> -- 
>  Jeff
> 
>  Jeff Abrahamson  <http://www.purple.com/jeff/>
> 
> 
> 
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