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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
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Configuring Optional Spanning-Tree Features
This chapter describes how to configure optional spanning-tree features on the Cisco ME 3400 Ethernet
Access switch. You can configure all of these features when your switch is running per-VLAN
spanning-tree plus (PVST+). You can configure only the noted features when your switch is running the
Multiple Spanning Tree Protocol (MSTP) or the rapid per-VLAN spanning-tree plus (rapid-PVST+)
protocol. On the Cisco ME switch, STP is enabled by default on network node interfaces (NNIs). It is
disabled by default, but can be enabled, on enhanced network interfaces (ENIs). User network interfaces
(UNIs) on the switch do not participate in STP. UNIs and ENIs on which STP is not enabled immediately
forward traffic when they are brought up.
For information on configuring the PVST+ and rapid PVST+, see Chapter 14, “Configuring STP.” For
information about the Multiple Spanning Tree Protocol (MSTP) and how to map multiple VLANs to the
same spanning-tree instance, see Chapter 15, “Configuring MSTP.”
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 Optional Spanning-Tree Features, page 16-1
• Configuring Optional Spanning-Tree Features, page 16-5
• Displaying the Spanning-Tree Status, page 16-11

Understanding Optional Spanning-Tree Features

These sections contain this conceptual information:
• Understanding Port Fast, page 16-2
• Understanding BPDU Guard, page 16-3
• Understanding BPDU Filtering, page 16-3
• Understanding EtherChannel Guard, page 16-3
• Understanding Root Guard, page 16-4
• Understanding Loop Guard, page 16-5