162
Chapter 3
Internet Protocols
Broadcast address for each subnet?
Valid hosts?
The following table shows the first seven subnet ranges, valid hosts, and
broadcast addresses.
Notice that for each subnet value in the third octet, you get subnets 0, 64,
128, and 192 in the fourth octet. This is true for every subnet in the third octet
except 0 and 255. I just demonstrated the 0-subnet value in the third octet.
But notice that for the 1 subnet in the third octet, the fourth octet has four
subnets: 0, 64, 128, and 192.
Practice Example #7B: 255.255.255.224 (/27)
This is done the same way as the preceding subnet mask, except that we just
have more subnets and fewer hosts per subnet available.
Subnets? 2
11
- 2 = 2046.
Hosts? 2
5
- 2 = 30.
Valid subnets? 256
- 224 = 32, 64, 96, 128, 160, 192. However, as
demonstrated above, both the 0 and 224 subnets can be used as long
as the third octet does not show a value of 0 or 255. Here's an example
of having no subnet bits in the third octet.
Broadcast address for each subnet?
Valid hosts?
The following table shows the first seven subnets.
Subnet
0.64
0.128
0.192
1.0
1.64
1.128
1.192
...
First host
0.65
0.129
0.193
1.1
1.65
1.129
1.193
...
Last host
0.126 0.190
0.254
1.62 1.126
1.190
1.254
...
Broadcast
0.127 0.191
0.255
1.63 1.127
1.191
1.255
...
Subnet
0.32
0.64
0.96
0.128
0.160
0.192
0.224
First host
0.33
0.65
0.97
0.129
0.161
0.193
0.225
Last host
0.62
0.94
0.126
0.158
0.190
0.222
0.254
Broadcast
0.63
0.95
0.127
0.159
0.191
0.223
0.255
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