Spanning Tree Protocol; Stp/Rstp Overview; Stp Terminology; Table 22 Stp Path Costs - ZyXEL Communications Dimension ES-2108 User Manual

This chapter introduces the Spanning Tree Protocol (STP).

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.
Note: 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; it is the bridge with the lowest identifier value
(MAC address).
Path cost is the cost of transmitting a frame onto a LAN through that port. It is assigned
according to the speed of the link to which a port is attached. The slower the media, the higher
the cost.

Table 22 STP Path Costs

LINK SPEED RECOMMENDED VALUE
Path Cost 4Mbps
Path Cost 10Mbps
Path Cost 16Mbps
Path Cost 100Mbps
Path Cost 1Gbps
Path Cost 10Gbps
Chapter 11 Spanning Tree Protocol

Spanning Tree Protocol

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ES-2108 Series User's Guide
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ALLOWED RANGE
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1 to 65535
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