Step 2 Write the mask bits of the same octet (11110000).
Step 3 Draw a vertical line to delineate the network-signi?¬?cant bits in the
assigned IP address. Put a line under the mask so that you can view the
signi?¬?cant bits in the IP address (10000000).
Step 4 Copy the signi?¬?cant bits four times.
Step 5 In the ?¬?rst line, de?¬?ne the network address by placing 0s in the remaining
host bits (10000000.00000000).
Step 6 In the last line, de?¬?ne the directed broadcast address by placing all 1s in
the host bits (10011111.11111111).
Step 7 In the middle lines, de?¬?ne the ?¬?rst and last host ID for this subnet??”
10000000.00000001 and 10011111.11111110.
Step 8 Increment the subnet bits by 1 to determine the next subnet address.
Repeat Steps 4 through 8 for all subnets (10100000.00000000).
Table 4-4 shows the range of subnets and broadcast addresses that would be available with
the given subnet mask.
Class A Example
In Figure 4-24, we will determine the addressing for a Class A network with a nondefault
mask. Given the address of 10.172.16.211 and knowing that the subnet mask is /18, you can
determine the subnet and host addresses for this network.
Table 4-4 Subnet Addresses Table
Subnet No. Subnet ID Host Range Broadcast
All 0s 172.
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