The prevalence of the Internet in business today raises many issues that
were unheard of a couple of years ago. One such issue is multi-homing, or
setting up and maintaining virtual servers on an NT Web server. For
organizations that provide Web services to others, multi-homing is a way to
configure one NT server to support several IP addresses and Internet domain
names (for more on IP addresses, see Mark Minasi, "How to Set up IP,"
February 1996; "NT Workstations Using an IP Router," May 1996; an "Unlock
Your Gateway to the Internet," June 1996). In this article, we will
describe what you can do with multi-homing, identify what you need for
multi-homing on an NT Web server, specify how you add multi-homing, and provide
tips for planning a multi-homing implementation.
What You Can Do
With multi-homing, you can house several
organizations' Web sites on one NT server and let each organization maintain its
identity. To the world, one NT Web server appears as multiple Web servers, each
with its own domain name. For example, Company A appears as www.companya.com and
Company B appears as www.companyb.com, although both share one Web server. This
method provides a cost-efficient way to connect several organizations to the
Web: You purchase one computer, one NT Server license, and one Web server
software component.
Multi-homing is not the same as having virtual paths on a Web server. With
virtual paths, every organization on the Web server shares one domain name. For
example, Company A appears as www.abc.com/~companya and Company B appears as
www.abc.com/~companyb.
Unix Internet Service Provider (ISP) aficionados consider a Unix platform
best for multi-homing because about 50 companies can be on a standard Unix box
and Unix people think only 15 or so can be on a comparably equipped NT box.
However, I know of one ISP that houses 70 virtual servers on one average NT box.
What You Need
Any time multiple organizations are on one
machine, you need sufficient RAM and hard disk. At a minimum, your NT Web server
must be a Pentium 120MHz, with 32MB of RAM and a 1GB to 2GB SCSI drive. Besides
this hardware, for this example, you need:
- a valid IP address for each domain name you register with InterNIC, the US
organization that manages domains on the Internet (for details, see the sidebar,
"Registering a Domain Name Is Easy," page 88)
- an NIC or Microsoft loopback adapter for testing
- Web server software (such as Internet Information Server--IIS--or Purveyor)
that supports virtual servers
- a modem (preferably, 28.8Kbits per second) or ISDN, an Internet connection,
and an ISP dial-up phone number
- a directory layout scheme such as D:\CompanyA, D:\CompanyB
The Set Up
Setting up multi-homing on your NT Web server is
easy. Just follow these steps.
Step 1 Obtain
a valid IP address for each organization on your Web server--you
usually get this address from your ISP. You also need an IP address for each
organization you add to your Web server. If an organization doesn't provide its
IP address, you can register and obtain one from InterNIC at the URL,
www.internic.net or rs.internic.net.
Step 2 Create
a partition on your server and a directory for each organization, to
separate the server's system files from each organization's data files (home
pages, File Transfer Protocol--FTP--files, Common Gateway
Interface--CGI--scripts, etc.). Suppose you create a D drive partition. For each
organization, you can create a subdirectory from the D drive's root. Meaningful
names help distinguish one organization from another at a glance.
Step 3 Install
an NIC in the Web server, and if you don't have an NIC, install NT's
loopback adapter for testing. To configure an NIC or the loopback adapter, go to
Main, Control Panel, Network, Add Adapter. Scroll through the list, select your
card, and click Continue. Follow the onscreen prompts and click OK when you
finish. You have to reboot the server for these configuration changes to take
effect.
Step 4 Install
and configure the TCP/IP protocol. Go to Main, Control Panel,
Network, Add Software, and choose TCP/IP Protocol and related components. Go to
the Advanced section of the TCP/IP configuration. Add up to five IP addresses
and subnet masks for each organization you plan to house. After you enter the
second IP address, Enable IP Routing changes from gray to black--mark
it. For more than five IP addresses, you manually add them in the Registry (see
the sidebar, "How to Set Up Virtual Domains," on page 90). A patch
from Microsoft lets you add up to 254 IP addresses. Your server will be limited
by its horsepower and the amount of traffic for each virtual Web server. (Note
that you install the IP address for your Web server in Step 6, not this one.)
After you finish adding each organization's IP address, reboot NT.
Step 5 Install
and configure Remote Access Service (RAS) if you haven't already
connected your modem to your Web server. Go to Main, Control Panel, Network, Add
Software; choose Remote Access Service. Select the appropriate modem and COM
port settings, and select Dial out and Receive calls. This setting lets
your Web server dial out to an ISP and lets each organization on your Web server
dial in to maintain its subdirectory. Select the TCP/IP protocol for dial out
and the protocols you want for dial in (the protocol depends on each
organization's needs). Reboot the server.