📄 content.html
字号:
<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; dash = contentID.indexOf('-'); sub1 = contentID.substring(0,dash); sub2 = contentID.substring(dash+1); numbackParams = "CHAPID=" + "knet-v214aCH47503" + "/RLOID=" + "knet-v214aRLO47534" + "/RIOID=" + "knet-v214aRIO121106"; ContentRef = "../../../../../"+ numbackParams + "/"+ sub1 +"/"+ sub2 +"/"; eval('parent.frames.content_frame.location.href="'+ContentRef+'content.html"'); eval('parent.frames.media_frame.location.href="'+ContentRef+'media.html"'); eval('parent.frames.navigation_frame.location.href="'+ContentRef+'contentresourcenav.html"'); top.currentSupport++; top.firstSupportPage = contentID; top.prevPage = contentID; top.contentResourceID = contentID; } 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_crf.html"'); chapter = "knet-v214aCH47503"; ch_dash = chapter.indexOf('-'); ch_sub1 = chapter.substring(0,ch_dash); ch_sub2 = chapter.substring(ch_dash+1); params = "CHAPID=" + chapter + "/RLOID=" + "knet-v214aRLO47534" + "/RIOID=" + "knet-v214aRIO121106"; returnRef = "../../../../../"+ params + "/"+ ch_sub1 +"/"+ ch_sub2 +"/pageframeset.html"; top.prevPage = returnRef; } function launchFile(filepath) { newWindow = window.open(filepath,"","top=70,left=120,width="+(screen.width*.50)+",height="+(screen.height*.50)+",resizable=yes,scrollbars=yes,toolbar=yes,menubar=yes,status=yes"); /* if (is.ie && filepath.lastIndexOf(".pdf") != -1) { pageTimer = setInterval("winLoadCheck()", 1000); } */ } function winLoadCheck() { if (newWindow.document.readyState == 'complete') { clearInterval(pageTimer); newWindow.location.reload(); } } // BrowserCheck Object // provides most commonly needed browser checking variables // 19990326 // Copyright (C) 1999 Dan Steinman // Distributed under the terms of the GNU Library General Public License // Available at http://www.dansteinman.com/dynapi/ function BrowserCheck() { var b = navigator.appName if (b=="Netscape") this.b = "ns" else if (b=="Microsoft Internet Explorer") this.b = "ie" else this.b = b this.v = parseInt(navigator.appVersion) this.ns = (this.b=="ns" && this.v>=4) this.ns4 = (this.b=="ns" && this.v==4) this.ns5 = (this.b=="ns" && this.v==5) this.ie = (this.b=="ie" && this.v>=4) this.ie4 = (navigator.userAgent.indexOf('MSIE 4')>0) this.ie5 = (navigator.appVersion.indexOf('MSIE 5.0')>0) this.ie55 = (navigator.appVersion.indexOf('MSIE 5.5')>0) if (this.ie5) this.v = 5 this.min = (this.ns||this.ie) } // automatically create the "is" object is = new BrowserCheck()</script> </head> <body onLoad="window.focus();" alink="#000000" vlink="#000000" link="#000000" bgcolor="#E7E7E7" background="../../../../../images/ccna/common/bg.gif"> <table width="100%" cellspacing="0" cellpadding="2" border="0"><tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="rlohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="rlohdr">3.1</td><td width="100%" class="rlohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="rlohdr">Basic LAN Devices</td> </tr> </table> </td> </tr> <tr> <td bgcolor="#000000"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td class="riohdr"><img height="1" width="2" border="0" src="../../../../../images/ccna/common/transdot.gif"></td><td valign="top" class="riohdr">3.1.5</td><td width="100%" class="riohdr"> <table width="90%" cellpadding="0" cellspacing="0" border="0"> <tr> <td class="riohdr">Repeaters</td> </tr> </table> </td> </tr> <tr> <td colspan="4"> <table width="90%" cellspacing="0" cellpadding="0" border="0"> <tr> <td class="smtext"> <p> </p><table cellpadding="0" cellspacing="0" width="100%" border="0" xmlns:java="http://xml.apache.org/xslt/java"> <tr> <td width="100%"><img height="10" width="1" border="0" src="../../../../../images/ccna/common/transdot.gif"></td> </tr> <tr> <td width="100%"> <table bgcolor="#000000" bordercolor="#000000" cellspacing="0" bordercolorlight="#000000" width="100%" border="0"> <tr> <td width="100%"> <table bgcolor="#FFFFFF" cellspacing="0" cellpadding="2" width="100%" border="0"> <tr> <td valign="middle"><img height="22" width="22" border="0" src="../../../../../images/ccna/common/inotes.gif"></td><td valign="middle"><span class="cstitle">Instructor Note</span></td> </tr> <tr> <td valign="top"> </td><td valign="top"><span class="cstext"> <p>The purpose of this target indicator is to allow the student to start recognizing repeaters on a logical topology, to describe how they really appear, and to briefly describe their function.</p> <p>A good class activity is to make flash cards -- with the device symbol on the front, and the device name, layer, and function on the back. Repeaters are Layer 1 devices, which regenerate and retime network signals so LANs can be extended to greater lengths. Regeneration means to restore an incoming digital signal with proper amplitude and duration and send it back out on the media. As a signal travels through the media, it may become distored by any number of processes.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>As mentioned on the network media page, there are many types of media, and each one has advantages and disadvantages. One of the disadvantages of the type of cable that we primarily use (CAT 5 UTP) is cable length. The maximum length for UTP cable in a network is 100 meters (approximately 333 feet). If we need to extend our network beyond that limit, we must add a device to our network. This device is called a <i>repeater.</i><img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121106/knet/v214adataimage1/1.gif" width="12" height="12"></p><p>The term repeater comes from the early days of visual communication, when a man situated on a hill would repeat the signal he had just received from the person on the hill to his left, in order to communicate the signal to the person on the hill to his right. It also comes from telegraph, telephone, microwave, and optical communications, all of which use repeaters to strengthen their signals over long distances.<img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121106/knet/v214adataimage2/2.gif" width="12" height="12"></p><p>The purpose of a repeater is to regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media. Watch out for the Four Repeater Rule for 10Mbps Ethernet. This is also known as the 5-4-3 Rule, when extending LAN segments. This rule states that you can connect five network segments end-to-end using four repeaters but only three segments can have hosts (computers) on them.</p><p>The term repeater traditionally meant a single port "in" and a single port "out" device. Almost all repeaters found on networks today are multiport devices, commonly known as hubs. Repeaters are classified as Layer 1 devices in the OSI model, because they act only on the bit level and look at no other information. <img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121106/knet/v214adataimage3/3.gif" width="12" height="12"> The symbol for repeaters is not standardized, therefore, you will use the symbol shown in the Figure throughout the CCNA curriculum.<img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121106/knet/v214adataimage1/1.gif" width="12" height="12"></p><p>For more information about commercially available repeaters, visit the websites listed below.</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://www.blackbox.com/">Blackbox Network Services</a></span></td> </tr> <tr> <td valign="middle" width="8%"> </td><td valign="middle" width="92%"><span class="smtext"><a target="_blank" href="http://www.warehouse.com/">Micro Warehouse</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
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -