D-Link DES-3326, Руководство пользователя

Страница: 92 / 425

24-port NWay Ethernet Switch User’s Guide
76 Switch Management and Operating Concepts
address space. A new scheme was introduced called Classless
Interdomain Routing (CIDR), as an extension of the classed
addressing scheme. CIDR allows greater control over the
number of IP addresses assigned to a subnet.
The classed IP addressing scheme will be discussed first.
IP addresses used within an intranetwork (within a company
network, for instance) have two parts – a network part and a
node part. The classed addressing scheme provides a method of
determining the information necessary to forward packets to and
from the subnetwork.
The classed scheme defines 5 address classes. The first 4 bits in
the IP address determine which class the IP address falls in.
?? Class A addresses begin with 0xxx, or 1 to 126 decimal.
??
Class B addresses begin with 10xx, or 128 to 191 decimal.
??
Class C addresses begin with 110x, or 192 to 223 decimal.
?? Class D addresses begin with 1110, or 224 to 239 decimal.
??
Class E addresses begin with 1111, or 240 to 254 decimal.
Addresses beginning with 01111111, or 127 decimal, are reserved
for loopback and internal testing on a local machine. (The
address 127.0.0.1 always points loops back to the local
computer – so you can always ping this address, if the network is
working). Class D addresses are reserved for multicasting.
Class E Addresses are reserved for future use.
So there are three classes available for the classed IP addressing
scheme. The classed IP addresses are divided into the network
part and the node (end station) part:
?? Class A NETWORK.node.node.node
??
Class B NETWORK.NETWORK.node.node
?? Class C NETWORK.NETWORK.NETWORK.node