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<html> <head> <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"> var pageLoaded = false; var current = ''; var currentChapter = 'knet-v214aCH47510'; function launchReference(rioID, rloID, chapterID) { contentID = "knet-v214aCV47051"; dash = contentID.indexOf('-'); sub1 = contentID.substring(0,dash); sub2 = contentID.substring(dash+1); numbackParams = "CHAPID=" + chapterID + "/RLOID=" + rloID + "/RIOID=" + rioID; ContentRef = "../../../../../"+ numbackParams + "/"+ sub1 +"/"+ sub2 +"/"; eval('top.frames.main_frame.location.href="'+ContentRef+'referencecontroller_pf.html"'); } function PrevPage() { top.currentSupport--; if (top.currentSupport <= 0) { returnContent(); } else { if (top.firstSupportPage == top.contentResourceID) { returnContent(); } else if (top.prevPage == quizID) { launchQuiz(); } else { launchReview(); } } } function launchReview(reviewID) { top.currentSupport = 0; chapterID = "knet-v214aCH47510"; nbparams = "CHAPID="+chapterID+"/RLOID="+"knet-v214aRLO47815"+"/RIOID="+reviewID; dash = chapterID.indexOf('-'); sub1 = chapterID.substring(0,dash); sub2 = chapterID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/"; //alert(ContentRef); eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); //added for navigating between Quiz and Review and back to regular Chapter pages top.currentSupport++; top.firstSupportPage = reviewID; top.prevPage = reviewID; top.contentResourceID = ''; } function launchQuiz(quizID) { top.currentSupport = 0; chapterID = "knet-v214aCH47510"; nbparams = "CHAPID="+chapterID+"/RLOID="+"knet-v214aRLO47821"+"/RIOID="+"knet-v214aRIO123683"; dash = chapterID.indexOf('-'); sub1 = chapterID.substring(0,dash); sub2 = chapterID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/"; //alert(ContentRef); eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); //added for navigating between Quiz and Review and back to regular Chapter pages top.currentSupport++; top.firstSupportPage = quizID; top.prevPage = quizID; top.contentResourceID = ''; } function returnContent() { rioID = top.currentPage; rloID = top.currentRLO; ContentID = top.currentChapter; top.firstSupportPage = ''; top.prevPage = ''; top.contentResourceID = ''; top.currentSupport = 0; nbparams = "CHAPID="+ContentID+"/RLOID="+rloID+"/RIOID="+rioID; dash = ContentID.indexOf('-'); sub1 = ContentID.substring(0,dash); sub2 = ContentID.substring(dash+1); ContentRef = "../../../../../"+ nbparams +"/"+ sub1 +"/"+ sub2 +"/" eval('top.frames.main_frame.location.href="'+ContentRef+'pageframesetrio.html"'); } </script> </head> <body leftmargin="20" topmargin="10" marginwidth="30" marginheight="10" bgcolor="#FFFFFF" onLoad="window.focus();" background="../../../../../images/ccna/common/lab/bglab.gif"> <table bgcolor="#000000" cellspacing="0" width="100%" border="0"> <tr> <td width="100%"> <table cellpadding="4" cellspacing="1" width="100%" border="0"> <tr> <td width="10%" bgcolor="#FFFFFF" valign="top"> <table cellpadding="0" cellspacing="0" width="100%" border="0"> <tr> <td width="33%"><script language="JavaScript"> //if (parent.parent.getTopName() == "chapterframeset") //{ var imgSource = '../../../../../images/ccna/common/lab/labback.gif'; document.write('<a href="javascript:PrevPage();">'); document.write('<img src="' + imgSource + '" border="0">'); document.write('</a>'); //} </script></td><td width="33%"></td> </tr> </table> <p> </p> </td><td bgcolor="#FFFFFF" valign="top"> <p align="left"> <span class="resourceTitle">10.4.1 IP address classes</span> </p><object height="100%" width="100%" codebase="http://active.macromedia.com/flash4/cabs/swflash.cab#version=4,0,0,0" classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"><param name="movie" value="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214aVID4956/10_4_1.swf"><param value="high" name="quality"> <embed height="100%" width="100%" pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" type="application/x-shockwave-flash" quality="high" src="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214aVID4956/10_4_1.swf"> </embed> </object>Instructor Note<p class="smtext">The purpose of this target indicator is that the students recognize class A, B, and C IP addresses. Students should be able to classify IP addresses as A, B, or C. They should also be able to label the octets "network" and "host" as appropriate for that address class. Emphasize that the network numbers are assigned by an external agency. Only the host numbers can be assigned locally.</p><p class="smtext">While you may have heard of other classless IP addressing schemes (such as CIDR, classless interdomain routing), the concepts of A, B, and C addresses are still widely used. Many questions on the CCNA exam assume classful addressing.</p><p class="smtext">The "lab", a paper-based activity, requires approximately 30 minutes. This TI is related to CCNA Certification Exam Objectives #29, #30, and #36.</p><p class="smtext">There are three classes of IP addresses that an organization can receive from the American Registry for Internet Numbers (ARIN) or the organization ISP. They are Class A, B, and C.<img border="0" src="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214adataimage1/1.gif" width="12" height="12"> ARIN now reserves Class A addresses for governments throughout the world (although a few large companies, such as Hewlett Packard, have received one in the past) and Class B addresses for medium-sized companies. All other requestors are issued Class C addresses.</p><a href="#" onClick="javascript:launchReference('knet-v214aRIO125373', 'null', 'null');void(null);">Lab Activity</a><p class="smtext">In this lab, students will learn the different classes of IP addresses and how TCP/IP networks operate.</p><p class="smtext"> <b>Class A</b><br>When written in a binary format, the first or furthest left bit of a Class A address is always 0. An example of a Class A IP address is 124.95.44.15. The first octet, 124, identifies the network number assigned by ARIN. The internal administrators of the network assign the remaining 24 bits. An easy way to recognize whether or not a device is part of a Class A network is to look at the first octet of its IP address, which will range from 0-126. (127 <i>does</i> start with a 0 bit, but has been reserved for special purposes.)</p><p class="smtext">All Class A IP addresses use only the first 8 bits to identify the network part of the address. The remaining three octets (24 bits) can be used for the host portion of the address. Because there are 24 bits available for host addresses, every network that uses a Class A IP address can have assigned up to 2<sup>24</sup> minus 2. That is, 16,777,214, possible IP addresses to devices that are attached to its network.<img border="0" src="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214adataimage2/2.gif" width="12" height="12"></p><p class="smtext"> <b>Class B</b><br>The first 2 bits of a Class B address are always 10 (one and zero). An example of a Class B IP address is 151.10.13.28. The first two octets identify the network number assigned by ARIN. The internal administrators of the network assign the remaining 16 bits. An easy way to recognize whether or not a device is part of a Class B network is to look at the first octet of its IP address. Class B IP addresses always have values ranging from 128 to 191 in their first octet.</p><p class="smtext">All Class B IP addresses use the first 16 bits to identify the network part of the address. The two remaining octets of the IP address can be used for the host portion of the address. Every network that uses a Class B IP address can have assigned up to 2<sup>16</sup> minus 2, or 65,534, possible IP addresses to devices that are attached to its network.<img border="0" src="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214adataimage3/3.gif" width="12" height="12"></p><p class="smtext"> <b>Class C</b><br>The first 3 bits of a Class C address are always 110 (one, one, and zero). An example of a Class C IP address is 201.110.213.28. The first three octets identify the network number assigned by ARIN. The internal administrators of the network assign the remaining 8 bits. An easy way to recognize whether or not a device is part of a Class C network is to look at the first octet of its IP address. Class C IP addresses always have values ranging from 192 to 223 in their first octet.</p><p class="smtext">All Class C IP addresses use the first 24 bits to identify the network part of the address. Only the last octet of a Class C IP address can be used for the host portion of the address. Every network that uses a Class C IP address can have assigned up to 2<sup>8</sup> minus 2, or 254, possible IP addresses to devices that are attached to its network.<img border="0" src="../../../../../CHAPID=knet-v214aCH47510/RLOID=knet-v214aRLO47815/RIOID=knet-v214aRIO123659/knet/v214adataimage4/4.gif" width="12" height="12"></p></td> </tr> </table> </td> </tr> </table> </body></html>⌨️ 快捷键说明
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