Cisco Catalyst 3120 User Manual

CHAPTER
17-1
Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
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17
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

Cisco Catalyst 3120 Specifications

General

Ports	24 x 10/100 + 2 x SFP
MAC Address Table Size	8K entries
Power Supply	AC 120/230 V (50/60 Hz)
Device Type	Switch
Form Factor	Rack-mountable
Routing Protocol	RIP-1, RIP-2, static IP routing
Remote Management Protocol	SNMP 1, RMON 1, RMON 2, RMON 3, RMON 9, Telnet, SNMP 3, SNMP 2c, HTTP, HTTPS, TFTP, CLI
Features	DHCP support, VLAN support, auto-negotiation, IPv6 support, Access Control List (ACL) support, Quality of Service (QoS), Rapid Spanning Tree Protocol (RSTP) support, Multiple Spanning Tree Protocol (MSTP) support, IGMP snooping
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.3z, IEEE 802.1D, IEEE 802.1Q, IEEE 802.3ab, IEEE 802.1p, IEEE 802.3x, IEEE 802.1w, IEEE 802.1x, IEEE 802.1s
Dimensions (H x W x D)	1.7 in x 17.5 in
Operating Temperature	32 °F
Operating Humidity	10%