ZyXEL Communications MGS-3712, User Manual

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MGS-3712/MGS-3012F User’s Guide
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H A P T E R
11
Spanning Tree Protocol
The Switch 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 Switch also allows you to set up multiple STP configurations (or trees). Ports can then be
assigned to the trees.
11.1 STP/RSTP Overview
(R)STP detects and breaks network loops and provides backup links between switches,
bridges or routers. It allows a switch 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 Switch 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.
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In this user’s guide, “STP” refers to both STP and RSTP.
11.1.1 STP Terminology
The root bridge is the base of the spanning tree.