Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 81
Determining a Common Prefix

The /27 prefix allows for an address range of:

20.127.1.32

20.127.1.64

20.127.1.96

20.127.1.128

20.127.1.160

20.127.1.192

20.127.1.224

Convert this to binary:

000010100.01111111.00000001.00100000 = 20.127.1.32

000010100.01111111.00000001.01000000 = 20.127.1.64

000010100.01111111.00000001.01100000 = 20.127.1.96

000010100.01111111.00000001.10000000 = 20.127.1.128

000010100.01111111.00000001.10100000 = 20.127.1.160

000010100.01111111.00000001.11000000 = 20.127.1.192

000010100.01111111.00000001.11100000 = 20.127.1.224

000010100.01111111.00000001.00000000 = Common prefix to all of the preceding addresses

Determining a Common Prefix

Therefore, applying rules 4 and 5, we have 20.127.1.0/24, which represents all of the addresses.