tailieunhanh - CompTIA Network+ Certification Study Guide part 32

CompTIA’s Network+ certification Study Guide part 32 is a globally-recognized, vendor neutral exam that has helped over 235,000 IT professionals reach further and higher in their careers. The 2009 Network+ exam (N10-004) is a major update with more focus on security and wireless aspects of networking. Our new study guide has been updated accordingly with focus on network, systems, and WAN security and complete coverage of today’s wireless networking standards. | 296 CHAPTER 7 TCP IP and Routing Table Binary and Decimal Values Bit number Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Notation 27 26 25 24 23 22 21 20 Decimal value 128 64 32 16 8 4 2 1 Table Setting Bits to Create Dotted Decimal Values Bit number Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Notation 27 26 25 24 23 22 21 20 Decimal value 128 64 32 16 8 4 2 1 Bit values for 132 1 0 0 0 0 1 0 0 the number is 1. How do we get to 2 We set the next bit bit 1 to 1 and reset bit 0 to 0. This is just like in the decimal numbering system in which you count in the right-most position from 0 to 9. After nine you move to the next position set it to 1 and reset the first position to 0 resulting in the decimal number 10. Binary works the same way except that each bit position can be only 0 or 1 thus you need more positions in order to represent decimal numbers. To create a binary number we set the desired bit to 1. For instance to represent the number 128 we would set the eighth position or bit 7 remember we re counting from 0 to 7 not 1 to 8 to 1. What if we wanted to create the number 132 We d set bit 7 and bit 2 to 1. The rest of the bits would remain 0 as shown in Table . Any number can be expressed this way limited only by the number of bits in a defined field in TCP IP we use only eight bits for each number . To convert a binary number to decimal add the value of each bit position set to 1. Thus the binary number 10000100 converts to decimal 132. To convert a decimal number to a binary number look at the decimal number and find the largest binary bit represented. If we want to convert 184 to binary we do the math shown in Table . For each number we subtract we set the corresponding bit to 1. Using this example 184 can be notated as 10111000 with the 128 32 16 and 8 bits set to 1 and the rest set to 0. As you become accustomed to working with both binary and decimal conversions you may not need to do this lengthy math eventually you might simply be .