ZyXEL Communications ONU-2024 Series, User Manual

Page: 95 / 268

ONU User’s Guide
95
C
H A P T E R
11
Spanning Tree Protocol
11.1 Overview
The ONU 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 ONU also allows you to set up multiple STP configurations (or trees). Ports can then be
assigned to the trees.
(R)STP detects and breaks network loops and provides backup links between switches,
bridges or routers. It allows a ONU 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 ONU 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 that then
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.
"
In this user’s guide, “STP” refers to both STP and RSTP.
11.1.1 What You Can Do in the STP Screens
• The Spanning Tree Configuration screen lets you select an STP mode ( Section 11.2 on
page 100 ).
• The Rapid Spanning Tree Configuration screen lets you select an RSTP mode ( Section
11.3 on page 100 ).
• The Rapid Spanning Tree Protocol Status screen lets you view the RSTP mode status
( Section 11.4 on page 102 ).
• The Multiple Spanning Tree Protocol screen lets you configure MSTP ( Section 11.5 on
page 103 ).
• The Multiple Spanning Tree Protocol Status screen lets you view the MSTP mode
status ( Section 11.6 on page 106 ).