6 April 2005

Fun With RFC2606 DNS Names

Posted under: at 16:09

RFC 2606 reserves several domain names that are safe to be used in documentation and testing. The idea is to avoid confusion and conflict when someone need to use domain names as example in documentation. For example: one might be tempted to use anything.com or something.com as example in documentation. But these domains are owned and someone might use those examples in verbatim without realizing that these domains are owned by somebody else.

The reserved domain names are:

  • .test (for testing)
  • .example (for documentation and examples)
  • .invalid (for domains that are sure to be invalid in examples)
  • .localhost (for loopback address)
  • .example.com
  • .example.net
  • .example.org

.test, .example and .invalid all don’t have records in the Internet name servers. .localhost does have an A record pointing to loopback address 127.0.0.1.

example.com, example.net and example.org all point to 192.0.34.43 and 193.0.0.236. When someone types http://example.net to their web browser, it will display the message:

You have reached this web page by typing “example.com”, “example.net”, or “example.org” into your web browser.

These domain names are reserved for use in documentation and are not available for registration. See RFC 2606, Section 3.

These addresses have their SMTP port filtered, probably to avoid getting unintended emails :).

According to Google, there are about 2010 pages pointing to example.com, example.net and example.org. But Google probably treats them as a single site. These sites has pagerank 7. Not bad for a web site that only contains only one simplistic web page.

What about ‘example’ domain for other non country TLDs? example.info, example.biz, example.coop, example.gov, example.info, example.int, example.name all are NXDOMAIN. example.aero returns two name servers, but both didn’t answer query for example.aero. example.edu points to two name servers, but both didn’t return any records for example.edu. example.museum has an A record but probably resulted from a wildcard address.

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