Справочное Руководство для Netopia 430 s

As you can see, subnet masks that allocate one, seven, or eight 
bits to subnets are useless for a Class C network. This is because 
binar y host addresses or subnet addresses that are composed of 
all zeros or all ones are reser ved for broadcasting (see 

). Class A or Class B networks, on the 

other hand, would still have many host numbers available if the 
network manager chose a subnet mask that allocated seven or 
eight bits to subnets.

1.

Decide on a subnet strategy

Your 25 IP hosts are arranged as follows: 10 on the third floor, eight 
on the four th floor, and seven on the fifth floor. Since you will need 
at least ten host addresses per subnet, the preceding table 
indicates that you must choose a subnet mask that allocates four or 
fewer bits to the subnet address. You decide to use a subnet mask 

Subnetting options for a Class C IP network

Subnet mask chosen

Number of bits for 

subnet number

Number of 

subnets possible

Number of 

hosts possible 

on each subnet

11111111.11111111.11111111.10000000
or 255.255.255.128

1

0

126

11111111.11111111.11111111.11000000
or 255.255.255.192

2

2

62

11111111.11111111.11111111.11100000
or 255.255.255.224

3

6

30

11111111.11111111.11111111.11110000
or 255.255.255.240

4

14

14

11111111.11111111.11111111.11111000
or 255.255.255.248

5

30

6

11111111.11111111.11111111.11111100
or 255.255.255.252

6

62

2

11111111.11111111.11111111.11111110
or 255.255.255.254

7

126

0

11111111.11111111.11111111.11111111
or 255.255.255.255

8

254

0