Re: Do DNS Servers cache?

Andrew Barton ( (no email) )
Fri, 10 Apr 1998 10:51:01 -0600

-----Original Message-----
From: David Payer <david.payer@IA-OMNI.COM>
To: <>
Date: Tuesday, April 07, 1998 9:47 AM
Subject: Re: Do DNS Servers cache?

>>My problem is...
>>I've tried bring up the 'new' sites from two other locations and it seems
>>they are still pointing to the old IP address. When I went into nslookup
>>defaulted to their own DNS servers - not mine), it reported the 'old' IP
>>Paul L.
>Paul, we had a similar problem. It appears that our upstream regional
>provider had not allowed us to be fully authoritative. For example, reverse
>lookups were only authoritative for them on many of the blocks of
>It caused a defininte problem for us.
>I contacted them, explained the problem and they were able to correct it in
>a day.
>You need to contact your upstream provider abou this. DNS transfers are
>usually complete in a day of them notifying you.

By the O'Reilly book, Non-authoritative answers are a common thing. It
simply means the the information is coming from the local cache. The first
time you nslookup the domain, it has to go out to a name server and find the
info. Authoritative. Your local DNS then caches the data so the next time
you do a lookup, if it is within the TTL, the cached data is used.

To get around this I will use the server statement at an nslookup prompt
like 'server' to point to another name server I know of.
This make nslookup point to a new server and get the information and so it
is Authoritative.

I have also seen it suggested that if you know ahead of time that you will
be doing some dns updates, shorten the TTL in the SOA record so that when
you make changes they will be updated more quickly.

Andrew Barton
RedShift Information Technology