Chapter 13 Spanning Tree Protocol
GS1915 Series User’s Guide
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C
HAPTER
13
Spanning Tree Protocol
13.1 Spanning Tree Protocol Overview
The Switch supports Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol (RSTP) as defined in
the following standards.
• IEEE 802.1D Spanning Tree Protocol
• IEEE 802.1w Rapid Spanning Tree Protocol
13.1.1 What You Can Do
• Use the
Rapid Spanning Tree Protocol Status
screen (
) to view the RSTP status.
• Use the
Rapid Spanning Tree Protocol
screen (
) to configure RSTP settings.
13.1.2 What You Need to Know
Read on for concepts on STP that can help you configure the screens in this chapter.
(Rapid) Spanning Tree Protocol
(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.
Note: In this user’s guide, “STP” refers to both STP and RSTP.
STP Terminology
The root bridge is the base of the spanning tree.
Path cost is the cost of transmitting a frame onto a LAN through that port. The recommended cost is
assigned according to the speed of the link to which a port is attached. The slower the media, the
