Creating Subnets - Novell NETWARE 6-DOCUMENTATION Manual

Creating Subnets

28
NetWare TCP/IP Administration Guide
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 nodes into separate networks reduces the
number of nodes on a data-link network. Fewer nodes generate less traffic
and, as a consequence, less congestion.
Reduce CPU use—Reducing CPU use on connected nodes is similar to
reducing congestion. More nodes on a network cause more broadcasts on
that network. Even if a broadcast is not sent to a particular node, each
node on a network must react to every broadcast before deciding to accept
it or discard it.
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.
For more information about creating subnets, see the following:
"Subnet Addresses and Masks" on page 29
"Subnet Zero" on page 32
"Variable Size Subnets" on page 32
"Assigning Subnet Addresses" on page 33
"Broadcast Addresses" on page 34
"Multicast Addresses" on page 34