Information Technology Reference
In-Depth Information
how you can break down a Class C network into one, two, four, or eight smaller subnets,
and it gives you the subnet masks, network numbers, broadcast addresses, and router
addresses. The first three bytes have simply been designated x.y.z. (Note that the table
assumes you can use the all-0s and all-1s subnets too.)
Table 8.5
Setting up Class C subnets
Remaining
number of IP
addresses
Number of
desired subnets
Network
number
Router
address
Broadcast
address
Subnet mask
1
255.255.255.0
x.y.z.0
x.y. z.1
x.y.z.255
253
2
255.255.255.128
x.y.z.0
x.y. z.1
x.y. z.127
125
255.255.255.128
x.y. z.128
x.y.z.129
x.y.z.255
125
4
255.255.255.192
x.y.z.0
x.y. z.1
x.y.z.63
61
255.255.255.192
x.y.z.64
x.y.z.65
x.y. z.127
61
255.255.255.192
x.y. z.128
x.y.z.129
x.y. z.191
61
255.255.255.192
x.y. z.192
x.y. z.19 3
x.y.z.255
61
8
255.255.255.224
x.y.z.0
x.y. z.1
x.y.z.31
29
255.255.255.224
x.y.z.32
x.y.z.33
x.y.z.63
29
255.255.255.224
x.y.z.64
x.y.z.65
x.y.z.95
29
255.255.255.224
x.y.z.96
x.y.z.97
x.y. z.127
29
255.255.255.224
x.y. z.128
x.y.z.129
x.y. z.15 9
29
255.255.255.224
x.y. z.16 0
x.y. z.161
x.y. z.191
29
255.255.255.224
x.y. z.192
x.y. z.19 3
x.y.z.223
29
255.255.255.224
x.y.z.224
x.y.z.225
x.y.z.255
29
For example, suppose you want to chop up a Class C network, 200.211.192. x , into two
subnets. As you can see in the table, you'd use a subnet mask of 255.255.255.128 for each
subnet. The first subnet would have the network number 200.211.192.0, router address
200.211.192.1, and broadcast address 200.211.192.127. You could assign IP addresses
200.211.192.2 through 200.211.192.126—that's 125 additional different IP addresses.
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