Spanning tree protocol must be enabled and BPDU guard and Portfast must be disabled on the upstream physical switch port for virtual machines that route or bridge traffic.

If an ESXi host guest VM is configured to perform a bridging function, the VM will generate BPDU frames to send out to the VDS. The VDS forwards the BPDU frames through the network adapter to the physical switch port. When the switch port configured with "BPDU guard" receives the BPDU frame, the switch will disable the port and the VM will lose connectivity. To avoid this network failure scenario while running a software-bridging function on an ESXi host, the "portfast" and "BPDU guard" configuration must be disabled on the port and spanning tree protocol must be enabled.