Subnetting
149
The 1s represent the subnet bits, and the 0s represent the host bits avail-
able in each subnet. 192 provides two bits for subnetting and six bits for
defining the hosts in each subnet.
What are the subnets? Since the subnet bits can't be both off or on at the
same time, the only two valid subnets are these two:
01000000
= 64 (all host bits off)
10000000
= 128 (all host bits off)
The valid hosts would be defined as the numbers between the subnets,
minus the all-host-bits-off and all-host-bits-on numbers.
To find the hosts, first find your subnet by turning all the host bits off,
then turn all the host bits on to find your broadcast address for the subnet.
The valid hosts must be between those two numbers. Table 3.5 shows the 64
subnet, valid host range, and broadcast address.
Table 3.6 shows the 128 subnet, valid host range, and broadcast
address.
T A B L E 3 . 5
Subnet 64
Subnet
Host
Meaning
01
000000 = 64
The network (do this first)
01
000001 = 65
The first valid host
01
111110 = 126
The last valid host
01
111111 = 127
The broadcast address
(do this second)
T A B L E 3 . 6
Subnet 128
Subnet
Host
Meaning
10
000000 = 128
The subnet address
10
000001 = 129
The first valid host
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