User's Manual

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Users Manual of CS-6306R
Figure 1.1 Port Fast
Instruction:
For the rapid convergent spanning tree protocol, RSTP and MSTP, can immediately bring an interface to the
forwarding state, and therefore there is no need to use Port Fast feature.
20.1.1.2 BPDU Guard
The BPDU guard feature can be globally enabled on the switch or can be enabled per port, but the feature
operates with some differences.
At the global level, you enable BPDU guard on Port Fast-enabled ports by using the spanning-tree portfast
bpduguard default global configuration command. Spanning tree shuts down ports that are in a Port
Fast-operational state if any BPDU is received on them. In a valid configuration, Port Fast-enabled ports do
not receive BPDUs. Receiving a BPDU on a Port Fast-enabled port means an invalid configuration, such as
the connection of an unauthorized device, and the BPDU guard feature puts the port in the error-disabled
state. When this happens, the switch shuts down the entire port on which the violation occurred.
To prevent the port from shutting down, you can use theerrdisable detect cause bpduguard shutdown
VLAN global configuration command to shut down just the offending VLAN on the port where the violation
occurred.
At the interface level, you enable BPDU guard on any port by using thespanning-tree bpduguard enable
interface configuration command without also enabling the Port Fast feature. When the port receives a
BPDU, it is put in the error-disabled state.
The BPDU guard feature provides a secure response to invalid configurations because you must manually
put the interface back in service. Use the BPDU guard feature in a service-provider network to prevent an
access port from participating in the spanning tree.