Allied Telesis SwitchBlade x3100 Series Manual page 381

Introduction
4.5 Spanning Tree Introduction: STP, RSTP, MSTP and BPDU
Cop
This chapter describes and provides configuration procedures for:
Spanning Tree Protocol (STP and RSTP)
•
Multiple Spanning Tree Protocol (MSTP)
•
BPDU COP
•
For detailed information about the commands used to configure spanning trees, see
List
4.5.1 Introduction
4.5.1.1 Spanning Tree Modes
STP can run in one of three modes: STP, RSTP or MSTP. A device running RSTP is compatible with other devices
running STP; a device running MSTP is compatible with other devices running RSTP or STP. By default, on a
device in MSTP mode each port automatically detects the mode of the device connected to it (MSTP, RSTP or
STP), and responds in the appropriate mode by sending messages (BPDUs) in the corresponding format. Ports
on a device in RSTP mode can automatically detect and respond to connected devices in RSTP and STP mode.
Particular ports can also be forced to only operate in a particular mode.
STP
•
The Spanning Tree Protocol (STP) is the original protocol defined by IEEE standard 802.1D-1988. It creates a
single spanning tree over a network.
By default, STP is disabled on all interfaces.
RSTP
•
Rapid Spanning Tree Protocol (RSTP) also creates a single spanning tree over a network. Compared with STP,
RSTP provides for more rapid convergence to an active spanning tree topology. RSTP is defined in IEEE standard
802.1D-2004.
By default, when STP is enabled, the system operates in RSTP mode.
MSTP
•
The Multiple Spanning Tree Protocol (MSTP) addresses the limitations in the previous spanning tree protocols,
STP and RSTP, within networks that use multiple VLANs with topologies that employ alternative physical links.
It supports multiple spanning tree instances on any given link within a network, and supports large networks by
grouping bridges into regions that appear as a single bridge to other devices.
Software Reference for SwitchBlade x3100 Series Switches (Layer Two Switching)
Introduction
Spanning Tree Command
4-61