ZyXEL Communications MES-2110 Guia do Utilizador descarregar pdf (Página 75)

MES-2110 User’s Guide

CHAPTER 10

Bridge

10.1 Overview

The Switch supports Rapid Spanning Tree Protocol (RSTP) as defined in the IEEE

802.1w Rapid Spanning Tree Protocol standard.

(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.

10.1.1 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 higher the cost.

Table 22 STP Path Costs

LINK

SPEED

RECOMMENDED

VALUE

RECOMMENDED

RANGE

ALLOWED

RANGE

Path

Cost

4Mbps 250 100 to 1000 1 to 65535

Path

Cost

10Mbps 100 50 to 600 1 to 65535

1 2 ... 70 71 72 73 74 75 76 77 78 79 80 ... 183 184

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ZyXEL Communications MES-2110 Guia do Utilizador Página 75