Configuring Stp Extensions - Cisco nexus 5000 series Configuration Manual

Configuring STP Extensions

This chapter contains the following sections:
•
Overview
Cisco has added extensions to Spanning Tree Protocol (STP) that make convergence more efficient. In some
cases, even though similar functionality may be incorporated into the IEEE 802.1w Rapid Spanning Tree
Protocol (RSTP) standard, we recommend using these extensions. All of these extensions can be used with
both RPVST+ and Multiple Spanning Tree Protocol (MST).
The available extensions are spanning tree port types, Bridge Assurance, BPDU Guard, BPDU Filtering, Loop
Guard, and Root Guard. Many of these features can be applied either globally or on specified interfaces.
Spanning tree is used to refer to IEEE 802.1w and IEEE 802.1s. If the text is discussing the IEEE 802.1D
Note
Spanning Tree Protocol, 802.1D is stated specifically.
Information About STP Extensions
Understanding STP Port Types
You can configure a spanning tree port as an edge port, a network port, or a normal port. A port can be in
only one of these states at a given time. The default spanning tree port type is normal. Depending on the type
of device to which the interface is connected, you can configure a spanning tree port as one of these port types.
Spanning Tree Edge Ports
Edge ports, which are connected to hosts, can be either an access port or a trunk port. The edge port interface
immediately transitions to the forwarding state, without moving through the blocking or learning states. (This
immediate transition was previously configured as the Cisco-proprietary feature PortFast.)
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