PVST protection

If a switch in the core of a network receives Per Vlan Spanning Tree (PVST) BPDUs and forwards the unrecognized PVST BPDUs on to MSTP-only switches, those switches then disconnect themselves from the network. This can create instability in the network infrastructure.

When the PVST protection feature is enabled on a port and a PVST BPDU is received on that port, the interface on which the PVST BPDU arrived is shut down, which isolates the sending switch from the rest of the network. An event message is logged and an SNMP notification trap is generated. The errant BPDU counter SwitchStpPortErrantBpduCounter is incremented. The PVST protection feature is enabled per-port.

Figure 18: PVST switch being isolated after sending a PVST BPDU

This is similar to the BPDU Guard feature where BPDU protection is applied to edge ports connected to end user devices that do not run STP. If STP BPDU packets are received on a protected port, the feature will disable that port and alert the network manager via an SNMP trap.