ZyXEL Communications OLT2406, User Manual

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Chapter 63 Spanning Tree Protocol
OLT2406 User’s Guide
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Spanning Tree Protocol
63.1 Overview
The OLT supports Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP) and Multiple
Spanning Tree Protocol (MSTP) as defined in the following standards.
• IEEE 802.1D Spanning Tree Protocol
• IEEE 802.1w Rapid Spanning Tree Protocol
• IEEE 802.1s Multiple Spanning Tree Protocol
The OLT also allows you to set up multiple STP configurations (or trees). Ports can then be assigned to the
trees.
63.2 STP/RSTP Overview
(R)STP detects and breaks network loops and provides backup links between switches, bridges or
routers. It allows a OLT to interact with other (R)STP-compliant switches in your network to ensure that
only one path exists between any two stations on the network.
The OLT uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allows faster convergence of the
spanning tree than STP (while also being backwards compatible with STP-only aware bridges). In RSTP,
topology change information is directly propagated throughout the network from the device that
generates the topology change. In STP, a longer delay is required as the device that causes a topology
change first notifies the root bridge and then the root bridge notifies the network. Both RSTP and STP flush
unwanted learned addresses from the filtering database. In RSTP, the port states are Discarding,
Learning, and Forwarding.
Note: In this user’s guide, “STP” refers to both STP and RSTP.
63.2.1 STP Terminology
The root bridge is the base of the spanning tree.