Ip Subnetting - Novell NETWARE 6-DOCUMENTATION Manual

IP Subnetting

two types. The Address Resolution Protocol (ARP) maps the IP address to the
physical address. ARP mapping is limited to networks that support hardware
broadcast.
One IP network can be divided into smaller networks, called subnets. The
following are reasons to divide your network:
Use multiple media—It can be impossible, inconvenient, or too
expensive to connect all nodes to a single network medium when these
nodes are too far apart or already connected to different media.
Reduce congestion—Traffic between nodes on a single network uses
network bandwidth. As a result, more bandwidth is required when you
have more nodes. Splitting a network reduces the number of nodes on a
data-link network. Fewer nodes generate less traffic and, as a
consequence, less congestion.
Reduce processor use—Because each node on a network must react to
every broadcast, reducing the number of nodes reduces processor use and
congestion.
Isolate a network—By splitting a large network into small networks, you
limit the impact of one network's problems on another. Such problems can
include network hardware failures, such as an open Ethernet tap, or
software failures, such as a broadcast storm.
Improve security—On a broadcast network medium such as Ethernet,
each node on a network has access to all packets sent on that network. By
enabling sensitive network traffic on only one network, other network
monitors can be prevented from accessing this sensitive traffic.
Make efficient use of IP address space—If you are using a Class A or B
network number and have multiple small physical networks, you can
divide the IP address space into multiple IP subnets and assign them to
individual physical networks. Another option is to obtain several Class C
network numbers, although this is less desirable.
Understanding Network Communications
15