3Com Switch 8800 Family Configuration Guide

72 CHAPTER 10: IP ADDRESS CONFIGURATION
Subnet and Mask Nowadays, with rapid development of the Internet, IP (V4) addresses are depleting
very in a few years. The traditional IP address allocation method wastes IP
addresses greatly. In order to make full use of the available IP addresses, the
concept of mask and subnet is proposed.
Tabl e 52 IP address classes and ranges
Network
class
Address
range
IP network
range
available Note
A
0.0.0.0 to
127.255.255.
255
1.0.0.0 to
126.0.0.0
Host ID with all the digits being 0 indicates
that the IP address is the network address,
and is used for network routing.
Host ID with all the digits being 1 indicates the
broadcast address, that is, broadcast to all
hosts on the network.
IP address 0.0.0.0 is used for the host that is
not put into use after starting up.
The IP address with network ID being 0
indicates the current network and its network
can be cited by the router without knowing its
network number.
The IP addresses with the format of 127.X.Y.Z
are reserved for self-loop test and the packets
sent to these addresses are not output to the
line. The packets are processed internally and
regarded as input packets.
B
128.0.0.0 to
191.255.255.
255
128.0.0.0 to
191.254.0.0
Host ID with all the digits being 0 indicates
that the IP address is the network address,
and is used for network routing.
Host ID with all the digits being 1 indicates the
broadcast address, that is, broadcast to all
hosts on the network.
C
192.0.0.0 to
223.255.255.
255
192.0.0.0 to
223.255.254.
0
Host ID with all the digits being 0 indicates
that the IP address is the network address,
and is used for network routing.
Host ID with all the digits being 1 indicates the
broadcast address, that is, broadcast to all
hosts on the network.
D
224.0.0.0 to
239.255.255.
255
None
Addresses of class D are multicast addresses,
among which:
■ IP address 224.0.0.0 is reserved and will
not be allocated. Those from 224.0.0.1 to
224.0.0.255 are reserved for routing
protocols and other protocols that are
used to discover and maintain routes.
■ Those from 239.0.0.0 to 239.255.255.255
are used for local multicast management.
■ Those from 224.0.0.255 to
238.255.255.255 are for users.
E
240.0.0.0 to
255.255.255.
254
None The addresses are reserved for future use.
Other
addresses
255.255.255.
255
255.255.255.
255
255.255.255.255 is used as a Local Area
Network (LAN) broadcast address.