CCNA 2.7.b: BPDU Guard

Overview:

BPDUGuard protects against loops that STP can't protect against when PortFast is enabled

Study Notes:

BPDU Guard complements the functionality of PortFast
On PortFast-enabled ports, BPDU Guard provides the protection against Layer 2 loops that STP cannot provide when STP PortFast is enabled
In a valid configuration, PortFast Layer 2 LAN interfaces (edge ports) do not receive BPDUs
When enabled on a port, BPDU Guard shuts down a port that receives a BPDU
When configured globally, BPDU Guard is only effective on ports in the operational PortFast (edge) state
Reception of a BPDU by a PortFast Layer 2 LAN interface signals an invalid configuration, such as connection of an unauthorized device
BPDU Guard provides a secure response to invalid configurations, because the administrator must manually put the Layer 2 LAN interface back in service
BPDU Guard can be configured at the interface level
When configured at the interface level, BPDU Guard shuts the port down as soon as the port receives a BPDU, regardless of the PortFast configuration
When enabled globally, BPDU Guard applies to all interfaces that are in an operational PortFast (edge) state.

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