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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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Switches are multiport bridges, hence they are Layer 2 devices which provide connectivity and dedicated bandwidth. They are also used to segment networks into smaller parts.</p> </span></td> </tr> </table> </td> </tr> </table> </td> </tr> </table><p>A switch, like a bridge, is a Layer 2 device. In fact a switch is called a multiport bridge, just as a hub is called a multiport repeater. The difference between the hub and switch is that switches make decisions based on MAC addresses and hubs do not make decisions. Because of the decisions that switches make, they make a LAN much more efficient. They do this by "switching" data only out the port to which the proper host is connected. In contrast, a hub will send the data out all of its ports so that all of the hosts have to see and process (accept or reject) all of the data.</p><p>At first glance switches often resemble hubs. Both hubs and switches have many connection ports, since part of their function is connectivity concentration (allowing many devices to be connected to one point in the network). The difference between a hub and a switch is what happens inside the device.</p><p>The purpose of a switch is to concentrate connectivity, while making data transmission more efficient. For now, think of the switch as something that is able to combine the connectivity of a hub with the traffic regulation of a bridge on each port. It switches frames from incoming ports (interfaces) to outgoing ports, while providing each port with full bandwidth (the transmission speed of data on the network backbone). You will learn more about this later.</p><p>The symbol for a switch is shown in the figure.<img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121109/knet/v214adataimage1/1.gif" width="12" height="12"> The arrows on top represent the separate paths data can take in a switch, unlike a hub, in which all data flows on all paths.<img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121109/knet/v214adataimage2/2.gif" width="12" height="12"><img border="0" src="../../../../../CHAPID=knet-v214aCH47503/RLOID=knet-v214aRLO47534/RIOID=knet-v214aRIO121109/knet/v214adataimage3/3.gif" width="12" height="12"></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.cisco.com/">Cisco Systems</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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