Layer 2 Redundancy

  • 为了可靠，引入冗余，进而引入环路
  • 可以参考David的视频课程，把防环关掉后的效果

03 Layer2 Loop - 图1

Layer 2 Loop

  • 导致的问题，广播风暴 和 未知单播

Spanning Tree Protocol

  • 2层防环
  • 思科设备里，默认开启这个协议

Bridge Protocol Data Unit

  • 承载STP 协议的数据包
  • BDPU 中包含ID，Priority等
  • 交换机通过1个特定的MAC地址，识别BPDU数据包
    • 0180 C200 0000

  1. GigabitEthernet1/0/1 receives the frame.

  2. The frame source MAC address does not exist in the MAC table of Multilayer Switch. Multilayer Switch adds a new MAC entry to its table.

  3. This is a unicast frame. Multilayer Switch looks in its MAC table for the destination MAC address.

  4. The frame destination MAC address is not in the MAC table. The Multilayer Switch floods the frame to all ports in the same VLAN except the receiving port.

  5. GigabitEthernet1/0/2 sends out the frame.

  6. GigabitEthernet1/0/3 sends out the frame.