Friday, June 25, 2010

DNS lookup questions

Question :
I have a very  basic question regarding the DNS lookup.
Few minutes ago I purchased a domain name through
and a only in a couple of minutes I can view it online.

I thought some routing tables need to be updated for a new website
to be viewable by common public. I am sure the routing tables
wouldn't have been updated all over the world in a couple of minutes.

What am I missing?

Answer 1 :
The issue you are thinking of occurs on existing domains when you move them.  It takes a while for the cache of your dns entries to expire.  When you register a new domain, there are no cached entries on DNS servers around the world so when you first request it your DNS server makes the full trip and you are good to go.

Answer 2 : 
Hi there.
There is a long nice story about root servers and DNS structure.
If you have the time, go to and read about it.

In a nutshell:
1. If you use same ISP as your hosting company, you will probably use the same DNS, and of course you will see the change real time.
2. If you use the most important ISP in your country, it is very likely that the DNS you use is the DNS responsible for the country domain. Also, your hosting company is very likely to use a very important DNS. Now, a user in the different side of the world that uses also an important DNS it's quite possible to see changes in a couple of minutes.

When I changed the routable IP for the main exchange server of a company, I had the pleasant surprise to see that the IP change for the domain was replicated from eastern europe to middle east in 15 minutes, because that company used the DNS responsible for the country.

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