ohohlfeld.com : blog
Networks in the Internet are—roughly speaking—grouped into Autonomous Systems (AS), which have a corresponding Autonomous System Number (ASN) as identifier. Using the routing prefixes (CIDR), IP addresses can be mapped to autonomous systems to find out which administration is running a certain network in which the requested service is provided. Lookups can be done in several ways. However, a compfortable one is provided by a Firefox browser Plugin called ASNumber. For each accessed website, AS related information will be displayed in the status bar of the Firefox web browser.
Please note that the resolution is done using a service hosted by the authors of ASNumber: eu.asnumber.networx.ch (if not cached locally). Thus, privacy related information about ones browsing behaviour may be logged on an external site and thus one may not enable the plugin all the time. An example request illustrating the lookup is given by this link.
