Cisco Systems N3KC3048TP1GE, N3KC3064TFAL3 manual Port States, Rapid PVST+ Port State Overview

Configuring Rapid PVST+

Understanding Rapid PVST+

are always in the blocking state. Designated ports start in the blocking state. The port state controls the operation of the forwarding and learning processes.

A port with the root or a designated port role is included in the active topology. A port with the alternate or backup port role is excluded from the active topology (see the following figure).

Figure 11: Sample Topology Demonstrating Port Roles

Port States

Rapid PVST+ Port State Overview

Propagation delays can occur when protocol information passes through a switched LAN. As a result, topology changes can take place at different times and at different places in a switched network. When a LAN port transitions directly from nonparticipation in the spanning tree topology to the forwarding state, it can create temporary data loops. Ports must wait for new topology information to propagate through the switched LAN before starting to forward frames.

Each LAN port on a software using Rapid PVST+ or MST exists in one of the following four states:

•Blocking—The LAN port does not participate in frame forwarding.

•Learning—The LAN port prepares to participate in frame forwarding.

•Forwarding—The LAN port forwards frames.

•Disabled—The LAN port does not participate in STP and is not forwarding frames.

When you enable Rapid PVST+, every port in the software, VLAN, and network goes through the blocking state and the transitory states of learning at power up. If properly configured, each LAN port stabilizes to the forwarding or blocking state.

	Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
72	OL-26590-01