DNS behavior question.

[Barry Margolin]

In article <gbpood$1ptg$1 at sf1.isc.org>,
 danjourno <danieljarrett74 at gmail.com> wrote:

> I'm no expert when it comes to DNS so forgive me if this seems a
> stupid question.
> 
> Yesterday one of my sites had a dns issue.. i think the servers went
> down. I couldn't get on to the hosting provider where the dns was
> hosted for over an hour so I redirected my domain to backup
> nameservers.. which also pointed to a new host server for my website.
> I left it like this for about 3 hours until the dns issue was resolved
> and then changed the domain to point back to the old nameservers and
> hence the old host server.
> 
> Anyway.. what I'm confused about is the behavior.. When i made the
> first change to point to the temporary nameserver and the initial
> nameserver was down the results were more or less instant. Whereas
> now, after I have switched it back I am still getting half of the site
> traffic going to one host server and half to the other almost 24 hours
> later. Is this normal behaviour?

Have you removed your zone from the backup nameservers?  If not, then 
all the sites that have those NS records cached will continue to get 
successful lookups.  And those lookups will probably include authority 
records that point to the backup nameservers, which will update the 
caches.  As a result, the NS records pointing to the backup nameservers 
will not time out of the caches very easily.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
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