Operation Manual – QinQ-BPDU TunnelingH3C S7500E 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 multicastover specific VLAN VPNs in the service provider network, so that the same,geographically dispersed customer network can implement consistent spanningtree calculation across the service provider network.2.1.2 Understanding BPDU TunnelingThe BPDU tunneling implements the following two functions:z BPDU isolationz BPDU transparent transmissionI. 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.
