Chapter 8: Desktop Configuration Servers
TCP/IP is able to link the world together into a global Internet because it does not depend on any
one physical network technology. It can run over the modem attached to a PC or over the
fiber−optic network attached to a super computer. It does this by creating a logical network on top of
the physical networks that is independent of the specific characteristic of any one network.
However, this flexibility comes at the price of complexity. It is more difficult to configure a computer
to run TCP/IP than it is to configure it for some other networks.
You're a technical person—that's why you run the network. Configuring TCP/IP may seem very
simple to you, but it can be a daunting task for the average user setting up a PC. If your network is
small, you can manually configure all of the desktop systems yourself. On a large network, manual
configuration becomes an impossible task. Even on a small network, fixing the configuration every
time a user upgrades is a thankless and boring job. The solution is to create a server that does this
job for you, which is the topic of this chapter.
Understanding Configuration Protocols
Protocol developers have worked to reduce the burden of manual system configuring for a long
time. Some of the documents that define the configuration protocols are more than 15 years old.
Surprisingly, these protocols have come into widespread use only in the past few years. This is
partly because the early users of the Internet were technical people who liked to configure their own
systems, and partly because of the tremendous growth in the number of systems running TCP/IP
that occurred at the end of the 1990s. Microsoft also deserves some credit for pushing hard to get
people to use Dynamic Host Configuration Protocol (DHCP), which is the best of the configuration
protocols. This section examines DHCP, as well as the other configuration protocols used to
configure desktop systems.
Bootstrap Protocol
Bootstrap Protocol
the information commonly used to configure TCP/IP—from the client's IP address to which print
server the client should use. The BootP protocol is designed to deliver this information to the client,
even though the client doesn't have an IP address.
Here's how it works. The BootP client broadcasts a BOOTREQUEST packet to UDP port 67, using
a special IP broadcast address of 255.255.255.255 that is called the limited broadcast address. The
broadcast address assigned in Chapter 2, "The Network Interface," with the ifconfig command was
made up of the network address with a host field of all ones; for example, 172.16.55.255. Clearly, a
BootP client that doesn't know the network address couldn't use such a broadcast address, which is
why the limited broadcast address is used.
(BootP) was the first comprehensive configuration protocol. It can provide all ofNote
address. For this reason, configuration servers are traditionally departmental
servers, with one server placed on each subnet. Later in this chapter, we will see
how relay servers can be used to support a centralized configuration server for
organizations that prefer centralization over distributed departmental servers.Unless specially configured to do so, routers do not forward the limited broadcast
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