stop DNS caching

[Chuck Yerkes]

Gutrot wrote:

> Hi,
>
> I'm trying my hand at making a Dynamic Dns server and am having some
> problems.  I am hoping that someone can answer some (hopefully) trivial
> questions for me.  I've read the DNS howto, tried 'man named' and
> searched some newsgroups and have not found what I'm looking for.
>
> Here's my question...  what exactly do Refresh, Retry, Expire and
> Minimum refer to.
>
> @                  IN SOA  ns1.mydomain.net. gut.mydomain.net. (
>                           19990527 ; Serial
>                           10800  ; Refresh
>                           3600    ; Retry
>                           604800  ; Expire
>                           86400 ) ; Minimum TTL
>
> 1.  Is it how long IP's will be cached on this my server?

> 2.  Or how long other nameserver will cache packets originating from my
>     domain?

Well, the DNS & BIND book covers it, as does the BOG (bind operations
guide), but in general,
you are SERVING this data.  You don't cache it at all.
- Refresh says how long secondaries should wait before doing a zone
transfer of the domain
- Retry says how long after a failure should it wait to try again
- Expire says how long until secondaries should stop serving un-refreshed
data.
- TTL is the time that the records live in cache on other servers (this
becomes the
   default TTL which can be overriden for specific records.

>
> I hope it's the second... because I'm having a problem with other
> nameservers caching the old IP address after I've gotten the new one and
> assigned it to a hostname.
>
> So.. if it's the first option.. then does anyone know how I could stop
> other nameservers from caching IP's?

You cannot stop servers from caching and you don't WANT to.  Otherwise your

name servers will start bleeding from use.  This is part of what makes DNS
scale -
unnecessary lookups are not overwhelming the 'net.

I've played with DDNS for (1) DHCP and fairly slowly changing names and
(2) internal hosts where names don't matter much (eg. a Desktop PC) and all

hosts use an authoritative name server (eg primary or secondary) for their
info - ones
where the DDNS is reflected in their maps.

chuck