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# Todd Lammle - page 11 / 54

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Subnet

Host

Meaning

11

000000 = 192

11

000001 = 193

The first valid host

11

111110 = 254

The last valid host

11

111111 = 255

114

Chapter 3

• IP Subnetting and Variable Length Subnet Masks (VLSMs)

## TABLE 3.6

Subnet 192

Hopefully, you understood what I was trying to show you. The example I presented only used 2 subnet bits, so what if you had to subnet using 9, 10, or even 20 subnet bits? Try that with the binary method and see how long it takes you.

In the following section, I’m going to teach you an alternate method of subnetting that makes it easier to subnet larger numbers in no time.

Since the CCNA exam gives you just over a minute for each question, it’s really important to know how much time you’ll spend on a subnetting question. That’s why committing as much as possible to memory, as I suggested earlier in the chapter, is vital. Using the binary method can take you way too long and you could fail the exam even if you know the material!

# The Fast Way: Subnetting a Class C Address

When you’ve chosen a possible subnet mask for your network and need to determine the num- ber of subnets, valid hosts, and broadcast addresses of a subnet that the mask provides, all you need to do is answer five simple questions:

• How many subnets does the chosen subnet mask produce?

• How many valid hosts per subnet are available?

• What are the valid subnets?