IP AddressesAn IP (Internet Protocol) Address is the number assigned to a computer that uses TCP/IP (Transport Control Protocol/Internet Protocol). This includes, of course, each and every computer that is connected to the Internet. The most important thing regarding IP addresses as far as the HelpDesk is concerned is that if a computer doesn't have the right IP address, none of its Internet applications will function properly.
Computers at JMU are assigned their IP addresses automatically by the bootp table. IP Addresses are composed of four sets of numbers in the range of 0-255. For example, the IP address of falcon.jmu.edu is 134.126.10.30 -- and it is the only computer on the Internet with this IP address. Some numbers (like 255 and 0, in particular) are reserved in certain cases.
Domains, domain names, and IP Addresses
IP Addresses are the way computers find each other on the Internet. Computers are good with numbers and poor with language. 134.126.10.30 makes a lot more sense to a computer than the phrase "JMU's general-usage UNIX machine, falcon." The other side of the coin is the fact that humans are good with language and poor (when compared to computers) with numbers. The average computer user can't be expected to remember that the host he or she wants to telnet to has an ip address of 134.126.10.30!This is why we use domain names to correspond to the IP addresses of computers on the internet. When you open netscape and ask it to view a web page on falcon.jmu.edu, Netscape first queries a domain name server (a computer responsible for knowing all the names and IP addresses of each computer for which it is responsible) to find out what the IP address of falcon.jmu.edu is. When the DNS server responds with the IP address, Netscape can easily find falcon and request the correct page.
IP addresses are not granted randomly, as it might seem. If that were the case, domain name lookups over the whole Internet would take up most of the time people would want to spend browsing the Web. Instead, each domain on the Internet is given a specific range of IP addresses. For example, JMU's computers can use IP addresses in the range of 134.126.0.1 through 134.126.254.254 (that's more than 64,000 computers!). This is because the domain jmu.edu is given the class B address 134.126.
IP Addresses come in three classes, A, B, and C. A class A address is for a large domain. For example, a class A domain could have the addresses 123.0.0.1 through 123.254.254.254 (16,387,064 computers!) A class B address would havve a range like JMU's (134.126.x.x). A class C address has only the last number to use (ie, 123.321.111.x).SEE ALSO:
E-mail comments to Lon Jarvis jarvislb@jmu.edu
last updated 3/17/00