【红头发ccna视频配套】第11章 2层交换技术知识 .pptVIP

Slide 3 of 3 Purpose: Emphasize: Note: 64 bytes is the minimum ethernet frame size. The command to switch the mode on the 1900 is: wg_sw_a(config)#switching-mode ? fragment-free Fragment Free mode store-and-forward Store-and-Forward mode Slide 1 of 1 Purpose: Emphasize: Layer 2 has no mechanism (like a TTL) to stop loops. Slide 1 of 3 Purpose: Emphasize: Broadcast frames are flooded. Slide 2 of 3 Purpose: Emphasize: Slide 3 of 3 Purpose: Emphasize: Layer 2 has no TTL mechanism to stop looping frames. Slide 1 of 1 Purpose: Emphasize: A looped topology is often desired to provide redundancy, but looped traffic is undesirable. The Spanning Tree protocol was originally designed for bridges. Today, it is also applied to LAN switches and routers operating as a bridge. STP ensures all bridged segments are reachable but any points where loops occur will be blocked. Slide 1 of 1 Purpose: Emphasize: The three general rules when dealing with STP: 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. ? 2002,张羿 Z_arthur@ ICND+HCNE—1-* ?2002. 张羿 1-* 第十一章层2交换技术 地址学习 帧的转发/过滤 环路防止 交换机的三个功能 交换机如何学习主机的位置 MAC地址表 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0 E1 E2 E3 A B C D 交换机如何学习主机的位置 主机A发送数据帧给主机C 交换机通过学习数据帧的源MAC地址，记录下主机A的MAC地址 对应端口E0 该数据帧转发到除端口E0以外的其它所有端口 (不清楚目标主机的单点传送用泛洪方式) 0260.8c01.1111 0260.8c01.2222 0260.8c01.3333 0260.8c01.4444 E0: 0260.8c01.1111 E0 E1 E2 E3 D C B A MAC地址表 交换机如何学习主机的位置 主机D发送数据帧给主机C 交换机通过学习数据帧的源MAC地址，记录下主机D的MAC地址对应端口E3 该数据帧转发到除端口E3以外的其它所有端口 (不清楚目标主机的单点传送用泛洪方式) 0260.8c01.1111 0