Specifications

Niagara Release 2.3
Revised: May 22, 2002 Niagara Networking & Connectivity Guide
Chapter 1 Understanding Networking and IP Addressing
Networking using IP
1–26
Most larger networks are made up of two types of devices: those that need a static
(non-changing) IP address because they are accessed frequently by other devices, and
most other hosts, which are rarely accessed by others. Hosts that are accessed
frequently (like servers and printers) are typically configured manually with a static
IP address. The remaining hosts are configured to receive a dynamic address.
Two common protocols used to dynamically assign addresses are BOOTP (Boot
Protocol) and DHCP (Dynamic Host Configuration Protocol). There are two
components to dynamic addressing: the server and the client.
Servers are set up with a pool of addresses to randomly distribute to clients (the host).
They can also provide subnet mask, default gateway information, and DNS server
information.
The host is configured to request this information from the server. When the host
boots, it sends a broadcast message requesting an IP address, and a server responds
with one of the numbers from the pool (and the remaining information). However,
the host is not necessarily guaranteed to receive the same IP address every time it
boots.
Note DHCP servers can be configured to provide a static IP address to a particular host.
For information on determining DHCP settings for a host, see the “ipconfig” section
on page 2-27.
Associating IP Addresses with Host Names
IP addresses may be easy for computers to work with, but they are hard for humans
to remember. This section addresses the technologies used to map the IP addresses
assigned to hosts to more friendly names. Once a host has a name, an application
running on another host can use the name rather than the IP address to request data.
The HOSTS File HOSTS files were the original mechanism used to resolve an IP address to a name.
The HOSTS file is a text file residing on each local machine. Each line of the text file
typically contains an IP address of a host and a name for it.
The primary limitation of this name resolution technique is that the HOSTS file is
only usable by the machine on which it resides. For example, you could add an entry
to Host A’s HOSTS file mapping Host B’s IP address to a name of “Pluto”. Any
application running on Host A could then contact Host B using the name “Pluto”.
However, Host B would not be addressable with “Pluto” by other hosts since the
mapping only resides in Host A’s local HOSTS file. That means another host wanting
to contact “Pluto” would need a similar entry in its local HOSTS file.
Therefore, HOSTS files are difficult to maintain when you have more than a few
hosts, and other technologies such as DNS, DDNS and WINS are often used instead.