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Now try some more subnet mask exercises using the data that follows:
Class B address
Class B address
1,000 hosts per subnet
25 subnets
Class C address
Class B address
45 hosts per subnet
4,000 hosts per subnet
192.168.0.0
Class B address
10 subnets
2,000 hosts per subnet
25 subnets
Here are the answers. If any of your answers are wrong, follow the previous examples
and try to work through them again.
Class B address
Class B address
1,000 hosts per subnet 255.255.252.0
25 subnets 255.255.248.0
Class C address
Class B address
45 hosts per subnet 255.255.255.192
4,000 hosts per subnet 255.255.240.0
192.168.0.0
Class B address
10 subnets 255.255.255.240
2,000 hosts per subnet
25 subnets 255.255.248.0
Applying Subnetting the Traditional Way
Sometimes subnetting can be confusing. After all, it can be quite difficult to remember all
of those numbers. You can step back a minute and take a look at the primary classes of
networks and how to subnet each one. Let's start with Class C because it uses only 8 bits
for the node address, so it's the easiest to calculate. In the following sections, I will explain
how to subnet the various types of networks.
Subnetting Class C
If you recall, a Class C network uses the first 3 bytes (24 bits) to define the network
address. This leaves you 1 byte (8 bits) with which to address hosts. So if you want to create
subnets, your options are limited because of the small number of bits available.
If you break down your subnets into chunks smaller than the default Class C, then
figuring out the subnet mask, network number, broadcast address, and router address can
be confusing. To build a sturdy base for subnetting, study the following techniques for
determining these special values for each subnet, but also learn and use the more efficient
technique presented in the later section “Quickly Identifying Subnet Characteristics Using
CIDR” and the earlier section “An Easier Way to Apply Subnetting.” Table 8.5 summarizes
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