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<html> <head> <meta content="en-us" http-equiv="Content-Language"> <meta content="text/html; charset=UTF-8" http-equiv="Content-Type"> <link type="text/css" rel="stylesheet" href="../../../../../css/ccna.css"> <script src="../../../../../js/framesetHelper.js" language="JavaScript"></script><script language="JavaScript"> window.scrollTo(0,0); function newPage(pageID) { alert("COMMING SOON!!\nThis feature is currently in development."); } function launchMoreInfo(oid) { dash = oid.indexOf('-'); sub1 = oid.substring(0,dash); sub2 = oid.substring(dash+1); // this is an URL base on the // system that generated the static // download of the curriculum. httpref = "http://nomar.sdf.cisco.com/servlet/org.cli.delivery.rendering.servlet.MIServlet/Static=true,LMSID=DTUI,Engine=dynamic,Theme=cnamstheme,Style=ccna,Language=en,Version=2,RootID=knet-v214aCV47051/CHAPID=null/RLOID=null/RIOID=null/"; newref = httpref + sub1 +"/"+ sub2 +"/moreinfoframeset.html"; //alert("new newref :\n" + newref); window.open(newref,'MoreInfo','toolbar=no,status=yes,menubar=no,location=no,scrollbars=yes,height=442,width=756,left=20,top=20,resizable=yes') } function launchContentResource(contentID) { top.currentSupport = 0; 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Draw upon the binary math that was taught in Chapter 1. Spend enough time on this diagram to assure that all students have mastered it. All future work involving IP addressing presupposes a complete understanding of the binary format and powers of two involved.</p> <p>This TI is related to CCNA Certification Exam Objectives #2, #29, and #36.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>An IP address is represented by a 32 bit binary number. As a quick review, remember that each binary digit (bit) can be only 0 or 1. In a binary number, the value of the right-most bit (also called the least significant bit) is either 0 or 1. The corresponding decimal value of each bit doubles as you move to the left in the binary number. So the <b> <u>decimal</u> </b> value of the 2nd bit from the right is either 0 or 2. The third bit is either 0 or 4, the fourth bit 0 or 8, and so on.</p><p>IP addresses are expressed as dotted-decimal numbers. The 32 bits of the address are broken into four octets (an octet is a group of 8 bits). The maximum decimal value of each octet is 255. The largest 8 bit binary number is 11111111. Those bits, from left to right, have decimal values of 128, 64, 32, 16, 8, 4, 2, and 1. Added together, they total 255.</p><p> <br>What is the decimal value of the highlighted octet in the graphic? What is the value of the bit on the far left side? The next bit? Since those are the only 2 bits on (or set), then the decimal value is 128+64=192.</p><table cellpadding="0" cellspacing="4" width="63%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td valign="middle" width="8%"><img height="23" width="23" src="../../../../../images/ccna/common/icon2.gif"></td><td valign="middle" width="92%"><span class="cstitle">Web Links</span></td> </tr> <tr> <td valign="middle" width="8%"> </td><td valign="middle" width="92%"><span class="smtext"><a target="_blank" href="http://oac3.hsc.uth.tmc.edu/staff/snewton/tcp-tutorial/">Introduction to the Internet Protocols</a></span></td> </tr> </table></td> </tr> </table> </td> </tr></table> <p> </p> <table width="100%" cellspacing="0" cellpadding="2" border="0" valign="bottom"> <tr> <td></td> </tr> </table> </body></html>⌨️ 快捷键说明
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