Understanding Rapid Pvst - Cisco N5010P-N2K-BE Software Configuration Manual

Information About Rapid PVST+
S e n d f e e d b a c k t o n x 5 0 0 0 - d o c f e e d b a c k @ c i s c o . c o m
Figure 8-2
DP
RP = Root Port
DP = Designated Port
When the spanning tree topology is calculated based on default parameters, the path between source and
destination end stations in a switched network might not be ideal. For instance, connecting higher-speed
links to a port that has a higher number than the current root port can cause a root-port change. The goal
is to make the fastest link the root port.
For example, assume that one port on Switch B is a fiber-optic link, and another port on Switch B (an
unshielded twisted-pair [UTP] link) is the root port. Network traffic might be more efficient over the
high-speed fiber-optic link. By changing the STP port priority on the fiber-optic port to a higher priority
(lower numerical value) than the root port, the fiber-optic port becomes the new root port.

Understanding Rapid PVST+

This section includes the following Rapid PVST+ topics:
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Overview
Rapid PVST+ is the IEEE 802.1w (RSTP) standard implemented per VLAN. A single instance of STP
runs on each configured VLAN (if you do not manually disable STP). Each Rapid PVST+ instance on a
VLAN has a single root switch. You can enable and disable STP on a per-VLAN basis when you are
running Rapid PVST+.
Rapid PVST+ is the default STP mode for the switch.
Note
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
8-6
Spanning Tree Topology
DP
DP
A
RP
DP
RP DP
RP
B C
Overview, page 8-6
Rapid PVST+ BPDUs, page 8-8
Proposal and Agreement Handshake, page 8-8
Protocol Timers, page 8-9
Port Roles, page 8-10
Port States, page 8-11
Synchronization of Port Roles, page 8-13
Detecting Unidirectional Link Failure, page 8-14
Port Cost, page 8-15
Port Priority, page 8-16
D
DP DP
Chapter 8 Configuring Rapid PVST+
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