Mac OS X 10.5 Help
Using a DNS server
A DNS (Domain Name System) server converts Internet names to IP addresses so you don’t have to know the IP address of a server you are trying to reach. If you are using the correct DNS server and have entered its address in Network preferences, you should be able to type www.apple.com into your browser, for example, and reach the Apple website. Without a DNS server, you would need to know the IP address of the server the Apple website resides on.
If you get a message such as “server not found” from your web browser when you try to visit a website, your computer may be unable to contact a DNS server. You may have entered the wrong DNS server address in your Network preferences or your DNS server may be having problems.
To find out which DNS server you should be using, check with your ISP or network administrator.
To check your DNS settings:
Choose Apple > System Preferences, and then click Network.
Select the network connection service you use to connect to the Internet (such as Ethernet) from the services list.
Make sure the IP address for the DNS server you want to use is entered correctly in the DNS Server field. You can correct the address if it’s wrong.
You can enter addresses for several servers by typing a comma between the addresses.
To edit more advanced DNS options, click Advanced.