View Full Version : Are DNS lookups generally real time?

02-04-2012, 03:05 AM
I just added a MX record to my zone file.

I queried a MX record for my domain name straight after, but nothing returned.
I am guessing the server I use for DNS lookup will be using a cached record, rather than looking up my DNS server real time, and that their cache will be flushed when their server does a periodic lookup on my DNS server, which will probably be within 48 hours, right?

02-04-2012, 03:14 AM
Yes. If the thousands of DNS around the world always did real time lookups of the information then there would be significant delays added to each and every web page access so as to slow the internet down due to the flood of requests that each nameserver would be receiving requesting the information.

DNS generally update at time intervals between every few minutes for some through every few weeks for others. Most update every few hours and so 99.9%+ will have updated within a couple of days.

02-04-2012, 03:44 AM
Thank you.

02-04-2012, 04:02 AM
Cool. My ISP DNS server has updated its cache with my new zone file.

There is something I am not happy about though... when I goto the URL 'mail.mydomain.com', it goes to my webpage 'mydomain.com', when it shouldn't be doing anything.
I added this to my zone file when adding the MX. Have I did it right?

IN MX 10 mail.mydomain.com.
mail IN A

How can I stop this behaviour?

02-04-2012, 06:12 AM
Like this:

IN MX 10 mydomain.com.