For those who haven't heard of TCP ports, here's an explanation. Because a server might be running several different pieces of server software—a Web server, a mail server, and a time server, for example—simply telling a piece of client software to go to www.acme.com doesn't give the client software all the information it needs to contact the appropriate server software. By default, a Web site runs on port 80, so when you point a Web client, such as Microsoft Internet Explorer (IE), to a particular DNS name, such as www.acme.com, the Web client assumes that you want it to contact the Web server at www.acme.com and at port 80. When the client software is Microsoft Outlook and it wants to download Internet email, the client needs to ask for port 110 on www.acme.com. When the client software is a program that synchronizes the client's clock with the server's clock, the client needs to ask for port 123 on the server. But those port numbers are default values, and most server and client software will let a client and server choose to use a nonstandard port instead of the default port.
Figure 1's TCP port this web site should use field lets you change the default port for your Web site. Let's say you decide to run www.oranges.com on the standard port 80 and to put www.apples.com on port 10000. If the Web server has the IP address 1.1.1.1, you'd create DNS entries that point both www.apples.com and www.oranges.com to 1.1.1.1. However, to override the default port, visitors to www.apples.com would have to use the URL http://www.apples.com:10000.
Requiring visitors to remember to add a port address to the URL isn't likely to pump up your daily Web traffic, so you're left with the third approach, which uses host header records. The Host Header for this site field lets the Web client—the browser—tell your Web server which site it wants to see. With host header records, you can host any number of Web sites on one Web server's port 80. The Web server can tell which Web site your visitor is looking for by examining what the Web browser asks it. Rather than simply saying, "Hey, Web server, would you show me default.htm?" the browser says, "Hey, Web server, would you show me default.htm on your www.oranges.com site?" The extra bit of information that identifies the particular site is called the host header record.
So why don't all Web sites use host header records? Nowadays, I'd guess that most sites do. But Web servers have understood host header records for only about 3 years, and even if your Web server understood host header records, early Web browsers (e.g., IE 2.0, Netscape 1.0) weren't smart enough to send them. Virtually every Web browser in use today knows about them, however, so you're safe with host headers on your site.
After you've gotten past that page in the wizard, the rest is easy. The wizard will ask you which directory holds your content and how to set security on the site (you can take the defaults).
Set Up DNS
Your Web sites are almost ready now, except for one more thing: DNS. Although your servers are prepared to respond to browsers near and far, those browsers can't send you requests if they can't find you. DNS's job is to make sure browsers can find your sites.
You need to register the apples.com and oranges.com domains with the Internet authorities, of course. Part of the domain registration process requires you to provide the names of two DNS servers that will host the address information for apples.com and oranges.com. Because those DNS servers must be connected to the Internet 24 * 7 * 365, many people choose not to run their own DNS servers but rather to let their ISP's DNS servers host their domains. Either way, you must put into the apples.com and oranges.com zones a host record that points to your Web server's IP address.
For the sake of completeness, I should mention that if you use separate IP addresses instead of host header records to segregate your Web sites, you must point each site's DNS record to the IP address that's associated with that site (in my example, 1.1.1.1 for www.apples.com and 1.1.1.2 for www.oranges.com). If you use separate ports at one IP address or host header records, you must point the Web sites' DNS records to the same IP address.