老大,关于STP的问题
ICND的3-49中为什么SWITCH Z FAIL 后SWITCH Y 成为 BOOT BRIDGE?<br>(按3-47说的X:Default Priority:32768;MAC: 0c0011111111<br> Y: Default Priority:32768;MAC: 0C0022222222)<br>Y的cost不是X高吗?<br><br>另:Nondesignated Port是不是cost最大的一个PORT?<br><IMG border=0 SRC=http://www.spoto.net/bbs/images/brow/confused_smile.gif> 还有一个问题,我看到一题:<br>What can you use to connect a user’s pc directly to a router?<br>A. Connect the PC's COM port to the router's console port using a straight-through cable.<br>B. Connect the PC's COM port to the router's console port using a crossover cable.<br>C. Connect the PC's COM port to the router's Ethernet port using a straight-through cable.<br>D. Connect the PC's Ethernet port to the router's Ethernet port using a crossover cable.<br>E. Connect the PC's Ethernet port to the router's Ethernet port using a rollover cable.<br>F. Connect the PC's Ethernet port to the router's Ethernet port using a straight-through cable.<br>Answer: D.<br><br>那么,crossover cable 与rollover cable 有什么不同?哪个才是交叉线? crossover cable是所谓的交叉线，就是12和36对调的线，平时经常会用到的；rollover好像叫做反转线，是把1～8完全反过来变成8～1的线，就是那种Cisco配给的天蓝色扁扁的线，其特点是一折就断…… sky<br>嘿嘿<br><br>我觉的cost是在有n条路时<br>选择路的概念<br>，而non.....是一条断路<br>应该不算<br><br> Nondesignated Port按什么原则来选?<br>crossover cable 与rollover cable分别在什么情况下用? <br><br> <BLOCKQUOTE><strong>引用</strong>：<HR Size=1>原文由 <b>sdspage</b> 发表:<br>crossover cable是所谓的交叉线，就是12和36对调的线，平时经常会用到的；rollover好像叫做反转线，是把1～8完全反过来变成8～1的线，就是那种Cisco配给的天蓝色扁扁的线，其特点是一折就断……<HR SIZE=1></BLOCKQUOTE><br>sdspage说的完全正确.<br>你知道crossover和straight throught的用法么? <BLOCKQUOTE><strong>引用</strong>：<HR Size=1>原文由 <b>sky</b> 发表:<br>Nondesignated Port按什么原则来选?<br>crossover cable 与rollover cable分别在什么情况下用? <br><br><HR SIZE=1></BLOCKQUOTE><br>这节课这次CCNA课程上有专门讨论过.<br>总之,一个原则,同类设备连接采用crossover cable,如路由器和路由器,路由器和PC.不同设备之间采用直连线.如PC和交换机,路由器和交换机...交换机和交换机直接根据连接不同的端口(uplink还是普通口)而定.<br>rollover cable很少用,一般做配置线,如路由器console口.<br> <BLOCKQUOTE><strong>引用</strong>：<HR Size=1>原文由 <b>sky</b> 发表:<br>ICND的3-49中为什么SWITCH Z FAIL 后SWITCH Y 成为 BOOT BRIDGE?<br>(按3-47说的X:Default Priority:32768;MAC: 0c0011111111<br> Y: Default Priority:32768;MAC: 0C0022222222)<br>Y的cost不是X高吗?<br><br>另:Nondesignated Port是不是cost最大的一个PORT?<br><img border=0 src=http://www.spoto.net/bbs/images/brow/confused_smile.gif onload="javascript:if(this.width>screen.width-300)this.width=screen.width-300"><HR SIZE=1></BLOCKQUOTE><br><br>Root bridge = Bridge with the lowest bridge ID<br><FONT size="7">Bridge ID =</FONT><img border=0 src=http://www.spoto.net/bbs/images/upfile/2003102215954.gif onload="javascript:if(this.width>screen.width-300)this.width=screen.width-300"><br>The default priority on the Catalyst 1900 is 32768 in decimal or 8000 in hex, the midrange value.<br><br>我现在手头里没有书,但如果是X:Default Priority:32768;MAC: 0c0011111111<br>Y: Default Priority:32768;MAC: 0C0022222222)的话,就是X为root.<br>另外."Y的cost不是X高吗?" 这叫做Y的bridge ID比X的大."<br><br>The three general rules when dealing with STP are as follows:<br>1. One root bridge per network. The root is the bridge with the lowest bridge ID. All the ports on the root bridge are designated ports (forwarding).<br>2. For every non-root bridge, there is a root port (forwarding). The root port is the port with the lowest accumulated path cost to the root bridge.<br>3. For every segment, there is only one designated port. The designated port forwards traffic for the segment. The designated port has the lowest accumulated path cost to the root bridge.<br><br><br><br>［此帖子已被 chinamoon 在 2003-10-2 22:01:17 编辑过］<br><br>［此帖子已被 chinamoon 在 2003-10-2 22:07:29 编辑过］ <BLOCKQUOTE><strong>引用</strong>：<HR Size=1>原文由 <b>sky</b> 发表:<br>Nondesignated Port按什么原则来选?<br>crossover cable 与rollover cable分别在什么情况下用? <br><br><HR SIZE=1></BLOCKQUOTE><br><img border=0 src=http://www.spoto.net/bbs/images/upfile/200310222851.gif onload="javascript:if(this.width>screen.width-300)this.width=screen.width-300"><br>如图:Non designated port关键有两点<br>1.在非root bridge上;<br>2.在线路block的那个端口上;<br><br>［此帖子已被 chinamoon 在 2003-10-2 22:10:53 编辑过］ 哦,THANKS!
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