Operation Manual – QinQ-BPDU TunnelingH3C S5500-EI Series Ethernet Switches Chapter 2 BPDU Tunneling Configuration2-1Chapter 2 BPDU Tunneling ConfigurationWhen configuring BPDU tunneling, go to these sections for information you areinterested in:z Introduction to BPDU Tunnelingz Configuring BPDU Isolationz Configuring BPDU Transparent Transmissionz Configuring Destination Multicast MAC Address for BPDU Tunnel Framesz BPDU Tunneling Configuration Example2.1 Introduction to BPDU Tunneling2.1.1 Why BPDU TunnelingTo avoid loops in your network, you can enable the spanning tree protocol (STP) onyour device. However, STP gets aware of the topological structure of a network bymeans of bridge protocol data units (BPDUs) exchanged between different devices andthe BPDUs are Layer 2 multicast packets, which can be received and processed by allSTP-enabled devices on the network. This prevents each network from correctlycalculating its spanning tree. As a result, when redundant links exist in a network, dataloops will unavoidably occur.By allowing each network to have its own spanning tree while running STP, BPDUtunneling can resolve this problem.z BPDU tunneling can isolate BPDUs of different customer networks, so that onenetwork is not affected by others while calculating the topological structure.z BPDU tunneling enables BPDUs of the same customer network to be broadcast ina specific VLAN in the provider network, so that the geographically dispersedcustomer networks of the same customer can implement consistent spanning treecalculation across the provider network.2.1.2 How BPDU Tunneling WorksThe BPDU tunneling implements the following two functions:z BPDU isolationz BPDU transparent transmissionThe work process of IGMP is as follows:I. BPDU isolationWhen a port receives BPDUs of other networks, the port will discard the BPDUs, so thatthey will not take part in spanning tree calculation. Refer to Configuring BPDU Isolation.
