Wave Wireless Networking SPEEDLAN TM 6000, Operator'S Manual

Page: 37 / 50

SPEEDLAN TM
37
Figure of Subnetting a Network
Still confused?
An easier method to explain this concept is to use the classic “mailing” analogy used in IP addressing.
Consider that this network, called Long Street, is four blocks long. There are 254 houses on Long Street,
and each block contains 64 houses. Houses 1 to 63 reside on Block A. Houses 64 to 127 reside on Block
B. Houses 128 to 191 reside on Block C. Houses 192 to 254 reside on Block D. Think of each block as a
subnet. This means that Blocks A, B, C, and D are all part of Long Street, which is also known as the
network in this example. The mailman would organize the letters (or IP addresses for network equipment)
by creating four piles (one for each block, or subnet). As soon as the mailman picks up Pile A in his hand, he
knows which block to turn on. This same reasoning applies to Piles B, C, and D as well. Router D knows
exactly which subnet to transfer (or turn) the packets to by reading its IP and subnet mask address. Note
that each subnet on this network is 255.255.255.192. Why is 192 the last octet in the subnet mask and not
64? The last octet, 192, is the mask that allows 64 “houses” to know that the mailman (or router) is coming
in advance. The “houses” will know it’s mailman “Jim” by looking at the IP number.
Note: If the network is managed by a Simple Network Management Protocol for local or Internet
access, each brouter must contain a unique IP Address. This is one of the benefits of static or dynamic
addressing.
Internet
Router D
Router B
Router C
Computer Computer
Computer
Computer
Computer Computer Computer
Computer Computer Computer
Long Street
Subnet A
IP Address: 195.172.3.1
Subnet Mask: 255.255.255.192
Subnet B
IP Address: 195.172.3.64
Subnet Mask: 255.255.255.192
Subnet C
IP Address: 195.172.3.128
Subnet Mask: 255.255.255.192
Subnet D
IP Address: 195.172.3.192
Subnet Mask: 255.255.255.192
Router A