DNS RESOLVING PROBLEMS

Kevin Darcy kcd at daimlerchrysler.com
Wed Sep 6 01:52:13 UTC 2000


The fact that you're having problems with the external CNAME but not
anything else in the zone would normally indicate that the problem is in
the domain containing the CNAME's target, i.e. everyone.net. But offhand,
everything looks fine with that domain. I can't believe that
*both* nameservers for the domain, which appear to be on totally separate
networks, are frequently and simultaneously failing to answer queries for
the domain.

As for your question about client caching, generally client-class
*machines*, e.g. PC's, don't cache DNS. However, a given client may be
behind a forwarding chain, where each machine, acting as a DNS client,
forwards queries to another machine. This is very common in firewalled
environments, for instance. In this case, the "clients" may also be
server-class machines, and may cache DNS responses. Modern nameserver
implementations even cache "negative" answers, i.e. the fact that a name
*doesn't* exist, which may possibly explain the behavior you are seeing
(although a timeout trying to talk to the authoritative servers for a
domain would generally *not* be negatively-cached in this way).


- Kevin

Johnny Human Torch wrote:

> Can someone help me here, at least understand what is going on:
>
> I have a site: jediportal.net, the zone looks like this:
>
> @  86400 IN SOA ns1.centralinfo.net. jedimaster.jediportal.net. (
>             2000090510   ; serial number
>             21600   ; refresh
>             10800   ; retry
>             604800   ; expire
>             43200)  ; ttl
> @  43200 IN NS  ns1.centralinfo.net.
> @  43200 IN NS  ns2.centralinfo.net.
> www 43200 CNAME jediportal.net.
> @ 43200 A 208.56.49.64
> @ 43200 MX 0 sitemail.everyone.net.
> jedi 43200 CNAME siteurl.everyone.net.
>
> Now it seems day to day it gets lost on my DNS server (which is not
> something I am hosting, it is my ISP).  The jediportal.net and
> www.jediportal.net work (most of the time), it is the
> jedi.jediportal.net CNAME.  It isnt a isolated coincidence either.  The
> same thing happens at work.  Is there something I am missing?  The
> strange thing is that when I do a NSLOOKUP, it resolves everything
> fine.  Is there something client side that isnt getting refreshed and
> therefore holding old pointers, thinking that the page didnt work last
> time so it wont work this time?
>
> Any suggestions would be helpful..
>
> thanks
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.






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