Cisco Nexus 5000 Series Switch CLI Software Configuration Guide, NX-OS 4.0(1a)N1 (OL-16597-01, January 2009)

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8-13
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
OL-16597-01
Chapter 8 Configuring Rapid PVST+
Information About Rapid PVST+
• Incorporates the end station location information into its address database.
• Receives BPDUs and directs them to the system module.
• Processes BPDUs received from the system module.
• Receives and responds to network management messages.
Disabled State
A LAN port in the disabled state does not participate in frame forwarding or STP. A LAN port in the
disabled state is virtually nonoperational.
A disabled LAN port performs as follows:
• Discards frames received from the attached segment.
• Discards frames switched from another port for forwarding.
• Does not incorporate the end station location into its address database. (There is no learning, so there
is no address database update.)
• Does not receive BPDUs from neighbors.
• Does not receive BPDUs for transmission from the system module.
Summary of Port States
Table 8-3 lists the possible operational and Rapid PVST+ states for ports and the corresponding
inclusion in the active topology.
Synchronization of Port Roles
When the switch receives a proposal message on one of its ports and that port is selected as the new root
port, Rapid PVST+ forces all other ports to synchronize with the new root information.
The switch is synchronized with superior root information received on the root port if all other ports are
synchronized. An individual port on the switch is synchronized if either of the following applies:
• That port is in the blocking state.
• It is an edge port (a port configured to be at the edge of the network).
If a designated port is in the forwarding state and is not configured as an edge port, it transitions to the
blocking state when the Rapid PVST+ forces it to synchronize with new root information. In general,
when the Rapid PVST+ forces a port to synchronize with root information and the port does not satisfy
any of the above conditions, its port state is set to blocking.
Table 8-3 Port State Active Topology
Operational Status Port State
Is Port Included in the
Active Topology?
Enabled Blocking No
Enabled Learning Yes
Enabled Forwarding Yes
Disabled Disabled No