Configuring Spanning Tree Protocol This chapter describes how to configure the Spanning Tree Protocol (STP) on port-based VLANs on the Catalyst devices. The device 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 device stack appears as a single spanning-tree node to the rest of the network, and all stack members use the same bridge ID.
Restrictions for Spanning Tree Protocol, on page 1 Information About Spanning Tree Protocol, on page 1 How to Configure Spanning Tree Protocol, on page 11 Monitoring Spanning Tree Protocol Configuration Status, on page 22 Additional References for Spanning Tree Protocol, on page 22 Feature History for Spanning Tree Protocol, on page 22 Restrictions for Spanning Tree Protocol • An attempt to configure a device as the root device fails if the value necessary to be the root device is less than 1. • If your network consists of devices that support and do not support the extended system ID, it is unlikely that the device with the extended system ID support will become the root device.
The extended system ID increases the device priority value every time the VLAN number is greater than the priority of the connected devices running older software. • The root device for each spanning tree instance should be a backbone or distribution device. Do not configure an access device as the spanning tree primary root. Information About Spanning Tree Protocol The following sections provide information about spanning tree protocol: Spanning Tree Protocol Spanning Tree Protocol (STP) is a Layer 2 link management protocol that provides path redundancy while preventing loops in the network.
For a Layer 2 Ethernet network to function properly, only one active path Configuring Spanning Tree Protocol 1