[TriLUG] OT: DSL for SOHO in Chapel Hill

[Ben Pitzer]

> Six years ago when I moved HAHT over to TWTC from UUNet I was using
> UUNet as a secondary DNS.  I shortened my TTL *and* left behind a box
> running multiple IP's and forwarding ports to our new domain.  My plan
> was to pull the box and cancel the UUNet service once the hits on the
> box dropped to near zero.
>
> The hits on that box dropped after the first day, but were steady after
> that.  After a month I traced down all the hits that were still going to
> that box as coming from folks using UUNet's DNS servers.  They refused
> to drop their Secondary for HAHT.  All told it took them 3 months to
> drop the old information out of their DNS.
>
> >From that day on, I've always kept the Secondary (and the Primary) on a
> box that I control.
>
> YMMV -  Jon Carnes

Naturally it took UUNet that long.  They were probably going on IPs (DNS via
the Wayback Machine), but the fact is that had you dropped that box that
UUNet has as a secondary, their servers would have performed a root lookup
and gotten your info immediately.

As for having DNS on different subnets, you're correct in that it's unlikely
that both boxes are going to go down at the same time on the same subnet.
My point is that what if the subnet goes down?  If the switch or router that
both DNS servers are on die, then your fscked.  Which is why you, in a real
enterprise situation, want to have them on different networks entirely.
Now, granted, if your web server is on the same subnet as the box that dies,
it won't matter.....unless someone is sending you mail.  In which case,
they'll be looking for your MX records.  If the router that died also has
your primary MX server, it obviously won't help, but at the very least that
server can find your backup MX server to cache the mail for you from the
secondary DNS that you also have on the different network from your
primaries.

Redundancy makes my brain swim in circles.

Regards,
Ben Pitzer

---------------------------------------------

"Those that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
 --Ben Franklin--