User Manual

SPEEDLAN 9000 Series Installation and Operation User Guide Version 3.03
Basics of IP Addressing 9-3
This definition is not random; it is based on the fact that routers by reading just the first
three octets of the address field designate which network class it belongs to. This
selection simplifies the way routers handle the messages (packets) and speed up the
forwarding process.
In fact, IP defines five classes:
•
Class A addresses uses 1 octet for the network portion and 3 octets for the
node (or host) section of the address. This provides up to 128 networks with
16.7 million nodes for each network.
• First octet is assigned as network address
• Remaining octets used for node addresses
• Format: network, node, node, node
• In IP address 49.22.102.70, "49" is network address and "22.102.70" is
the node address—all machines on this network have the "49" network
address assigned to them
• Maximum of 224 or 16,777,216 nodes
• Class B addresses uses 2 octets for the network portion and 2 octets for the
node (or host) section of the address. This provides up to 16,384
networks with 64,534 nodes for each network.
• First 2 octets are assigned as network address
• Remaining octets used for node addresses
• Format: network, network, node, node
• In IP address 130.57.30.56, "130.57" is the network address, and
"30.56" is the node address
• Maximum of 216 or a total of 65,534 nodes
• Class C addresses use 3 octets for the network portion and 1 octet for the
node (or host) section of the address. This provides 16.7 million networks with
256 nodes for each network.
• First three octets are assigned as network address
• Remaining octet used for node address
• Format: network, network, network, node
• In IP address 192.0.2.102, "192.0.2" is the network address, and "102" is
the node address