How to tell to Search Engines that 2 domain names are the same website?

Question

If I have 2 domains names that points to same website. By example: microsoft.com and microsoft.net both points to microsoft.com.

How search engines can distinguish that these 2 websites are the same websites and not a duplicate content?

My question is because I know that Google, by example, have an duplicate content filter, and I want know I will do to declaratively say that the 2 domains are the same and are not duplicate content websites.

Thanks!

Answer 1

Choose which is to be the primary domain and then implement a 301 redirect on the other.

Answer 2

Is it important that the user always stays at the domain entered, or are the second merely an alias for the first? If the latter is the case, you could do a HTTP redirect to the desired domainname, when the user visits one of the aliases.

EDIT: Guess Mat beat me to it. :-)

Answer 3

You can establish a permanant forward (301) with most domain hoster.

For subdomains, you can normally have an HttpHandlers that take care of that.

Answer 4

like guys says use 301 header to redirect. but also try to put a robot.txt to deny bots access and avoid have duplicate content

Answer 5

make one site a 301 redirect to the other but do-not attempt the idiotic idea of a robots.txt {as for 1 if the secondary site is a 301 to the "real" site a robots.txt couldn't exist as all requests for any content are directed at the primary, that means everything including a robots.txt

thus no duplicate content anywhere all content on one site only the other just says {your in the wrong place go here instead}