IP Address Range for Switched Subnet in Figure 2.2

TABLE 2 . 7 IP Address Range for Switched Subnet in Figure 2.2
3rd Octet
128 64 32 16 8 4 2 1
4th Octet
128 64 32 16 8 4 2 1
Decimal IP Address
(Last 16 bits in bold)
Subnet mask 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 255.255.255.248
Subnet 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 172.16.0.8
First IP in range 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1 172.16.0.9
Last IP in range 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 172.16.0.14
Broadcast 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 172.16.0.15
Again, subtracting 248 from 256 leaves a value of 8, our increment. The first valid value of the
fourth octet, as always, is 0, but that’s already taken. Add 8, and the next subnet boundary is 8.
Because the 0 subnet was based on an increment of 4, we are fine placing this subnet at 8. In fact,
there is another two-host subnet at 4, which we had to skip—that can be used in the future.
Eliminating host IP addresses that contain all 1s and all 0s, as before, we discover that our valid
IP address range for this segment is 172.16.0.9–172.16.0.14. The broadcast address is all host bits
on, or 172.16.0.15, which is also one less than the next subnet boundary of 172.16.0.16, found
by using our increment of 8.
Now we will perform the same steps on the Ethernet user segment, as shown in Table 2.8,
and the server farm segment, as shown in Table 2.9.