老大,关于STP的问题

sky · 发表于 2003-10-2 09:45:42

ICND的3-49中为什么SWITCH Z FAIL 后SWITCH Y 成为 BOOT BRIDGE? (按3-47说的X:Default Priority:32768;MAC: 0c0011111111 Y: Default Priority:32768;MAC: 0C0022222222) Y的cost不是X高吗? 另:Nondesignated Port是不是cost最大的一个PORT? <IMG border=0 SRC=http://www.spoto.net/bbs/images/brow/confused_smile.gif>

sky · 发表于 2003-10-2 17:03:35

还有一个问题,我看到一题: What can you use to connect a user’s pc directly to a router? A. Connect the PC's COM port to the router's console port using a straight-through cable. B. Connect the PC's COM port to the router's console port using a crossover cable. C. Connect the PC's COM port to the router's Ethernet port using a straight-through cable. D. Connect the PC's Ethernet port to the router's Ethernet port using a crossover cable. E. Connect the PC's Ethernet port to the router's Ethernet port using a rollover cable. F. Connect the PC's Ethernet port to the router's Ethernet port using a straight-through cable. Answer: D. 那么,crossover cable 与rollover cable 有什么不同?哪个才是交叉线?

sdspage · 发表于 2003-10-2 17:16:47

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……

x3 · 发表于 2003-10-2 17:51:39

sky 嘿嘿 我觉的cost是在有n条路时 选择路的概念 ，而non.....是一条断路 应该不算

sky · 发表于 2003-10-2 20:09:47

Nondesignated Port按什么原则来选? crossover cable 与rollover cable分别在什么情况下用?

chinamoon · 发表于 2003-10-2 21:48:58

<BLOCKQUOTE>引用：<HR Size=1>原文由 sdspage 发表: 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> sdspage说的完全正确. 你知道crossover和straight throught的用法么?

chinamoon · 发表于 2003-10-2 21:52:45

<BLOCKQUOTE>引用：<HR Size=1>原文由 sky 发表: Nondesignated Port按什么原则来选? crossover cable 与rollover cable分别在什么情况下用? <HR SIZE=1></BLOCKQUOTE> 这节课这次CCNA课程上有专门讨论过. 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. rollover cable很少用,一般做配置线,如路由器console口.

chinamoon · 发表于 2003-10-2 22:00:08

<BLOCKQUOTE>引用：<HR Size=1>原文由 sky 发表: ICND的3-49中为什么SWITCH Z FAIL 后SWITCH Y 成为 BOOT BRIDGE? (按3-47说的X:Default Priority:32768;MAC: 0c0011111111 Y: Default Priority:32768;MAC: 0C0022222222) Y的cost不是X高吗? 另:Nondesignated Port是不是cost最大的一个PORT? <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> Root bridge = Bridge with the lowest bridge ID Bridge ID =<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"> The default priority on the Catalyst 1900 is 32768 in decimal or 8000 in hex, the midrange value. 我现在手头里没有书,但如果是X:Default Priority:32768;MAC: 0c0011111111 Y: Default Priority:32768;MAC: 0C0022222222)的话,就是X为root. 另外."Y的cost不是X高吗?" 这叫做Y的bridge ID比X的大." The three general rules when dealing with STP are as follows: 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). 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. 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. ［此帖子已被 chinamoon 在 2003-10-2 22:01:17 编辑过］ ［此帖子已被 chinamoon 在 2003-10-2 22:07:29 编辑过］

chinamoon · 发表于 2003-10-2 22:09:59

<BLOCKQUOTE>引用：<HR Size=1>原文由 sky 发表: Nondesignated Port按什么原则来选? crossover cable 与rollover cable分别在什么情况下用? <HR SIZE=1></BLOCKQUOTE> <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"> 如图:Non designated port关键有两点 1.在非root bridge上; 2.在线路block的那个端口上; ［此帖子已被 chinamoon 在 2003-10-2 22:10:53 编辑过］

sky · 发表于 2003-10-3 09:41:56

哦,THANKS!

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[讨论/求助] 老大,关于STP的问题