Cisco Catalyst 3120

CHAPTER
17-1
Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
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Configuring STP
This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the
switch. The switch can use either the per-VLAN spanning-tree plus (PVST+) protocol based on the IEEE
802.1D standard and Cisco proprietary extensions, or the rapid per-VLAN spanning-tree plus
(rapid-PVST+) protocol based on the IEEE 802.1w standard. A switch stack appears as a single
spanning-tree node to the rest of the network, and all stack members use the same bridge ID. Unless
otherwise noted, the term switch refers to a standalone switch and to a switch stack.
For information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs
to the same spanning-tree instance, see Chapter 18, “Configuring MSTP.” For information about other
spanning-tree features such as Port Fast, UplinkFast, root guard, and so forth, see Chapter 19,
“Configuring Optional Spanning-Tree Features.”
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
• Understanding Spanning-Tree Features, page 17-1
• Configuring Spanning-Tree Features, page 17-12
• Displaying the Spanning-Tree Status, page 17-24
Understanding Spanning-Tree Features
These sections contain this conceptual information:
• STP Overview, page 17-2
• Spanning-Tree Topology and BPDUs, page 17-3
• Bridge ID, Switch Priority, and Extended System ID, page 17-4
• Spanning-Tree Interface States, page 17-5
• How a Switch or Port Becomes the Root Switch or Root Port, page 17-8
• Spanning Tree and Redundant Connectivity, page 17-8
• Spanning-Tree Address Management, page 17-9
• Accelerated Aging to Retain Connectivity, page 17-9
• Spanning-Tree Modes and Protocols, page 17-10