I have some questions on Week 5 short lecture on Internet Primer, in particular on the host and ip address table that was being showed at 11.37 of the video. The questions are as follow:

Snapshot 1

Snaphsot 2

In the the attached pictures: 1. What does io-in-f138.1e100.net really refers to in the 1st picture?

  1. From David's lecture, I understood that ip address will map to a particular domain name. But why in this case it is being mapped to io-in-f138.1e100.net instead of google.com (as in picture 1)? I did tried to search for io-in-f138.1e100.net in the address bar, but it returned a 404 Not found error.

  2. How does io-in-f138.1e100.net being translate to google.com as in picture 2?

Thanks alot!

1 Answer 1


The io-in-f138.1e100.net or more generally the domain 1e100.net is used by Google for the purpose of identifying the servers in their network and therefore it maps to a Google server. The Google Help article shall dispense you more information.

Technically, multiple fully qualified domain names (FQDNs) could resolve to the same IP address since it would be really wasteful to have one server per each FQDN being served. This is made possible by utilisation of a mechanism known as Virtual Hosting particularly in this case Name-Base virtual hosting.

Well, its quite the opposite. A request destined to google.com would hit one of the servers name under the root domain 1e100.net. For the purpose of manifestation you could utilise the following command which should ultimately serve you the Google homepage;

curl -H 'Host: www.google.com' io-in-f138.1e100.net

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .