Cisco Catalyst 2960 Series, Configuration Manual

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Information About Optional Spanning-Tree Features
PortFast
PortFast immediately brings an interface configured as an access or trunk port to the forwarding state from a
blocking state, bypassing the listening and learning states.
You can use PortFast on interfaces connected to a single workstation or server to allow those devices to
immediately connect to the network, rather than waiting for the spanning tree to converge.
Figure 20: PortFast-Enabled Interfaces
Interfaces connected to a single workstation or server should not receive bridge protocol data units (BPDUs).
An interface with PortFast enabled goes through the normal cycle of spanning-tree status changes when the
switch is restarted.
You can enable this feature by enabling it on either the interface or on all nontrunking ports.
Related Topics
Enabling PortFast , on page 302
Restriction for Optional Spanning-Tree Features, on page 287
BPDU Guard
The Bridge Protocol Data Unit (BPDU) guard feature can be globally enabled on the switch or can be enabled
per port, but the feature operates with some differences.
When you enable BPDU guard at the global level on PortFast edge-enabled ports, spanning tree shuts down
ports that are in a PortFast edge-operational state if any BPDU is received on them. In a valid configuration,
PortFast edge-enabled ports do not receive BPDUs. Receiving a BPDU on a Port Fast edge-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.
When you enable BPDU guard at the interface level on any port without also enabling the PortFast edge
feature, and the port receives a BPDU, it is put in the error-disabled state.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
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Information About Optional Spanning-Tree Features