Using Cornell's DNS Servers

A machine called a domain name system (DNS) server is a vital part of the infrastructure that personal computers connected to the Internet rely on for Internet-based communications. Cornell's three DNS servers have the following addresses:

CIT strongly recommends that all three servers be entered into every computer's configuration so that if one DNS server is not reachable, the computer can find the other servers. To make sure that your computer's settings refer to all three of Cornell's DNS servers, see the "Get Online" instructions for the type of connection you are using, for example:

• Ethernet - on-campus wired
• RedRover on-campus wireless
• EZ-Remote modem dial-up

About the Domain Name System (DNS)

Every computer connected to the Internet must have a unique address, termed an IP address, in order to communicate with other computers on the Internet. IP addresses are numeric and consist of four sets of numbers, such as 128.253.242.110.

Because few people can memorize many IP addresses, we rely on "host names" and "domain names" to replace them; for example, when we want to connect to the CUinfo web site, we enter cuinfo.cornell.edu (the host name "cuinfo" followed by the domain name "cornell.edu") instead of 128.253.242.110.

Although the more meaningful names are easier for people to remember, computers need to translate these names into numeric IP addresses. To perform this translation, a personal computer contacts another computer, called a domain name system (DNS) server, which maintains a complete, up-to-date list of IP addresses and corresponding names for all of the computers on the Internet. The personal computer only needs to keep track of the IP addresses of one or more DNS servers.

Sometimes you may see a "not found" message when you enter a host name and domain name. If you are certain that you typed the names correctly, the problem could be that the host and domain names are new and have not yet been added to the DNS server's list. When this happens, you may be able to reach the computer you are trying to contact if you enter its numeric IP address instead of its host and domain names.