ZyXEL Communications G-3000H Manuel D’Utilisation

G-3000H User’s Guide

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Chapter 5 Wireless Configuration

STP detects and breaks network loops and provides backup links between switches, bridges or 
routers. It allows a bridge to interact with other STP-compliant bridges in your network to 
ensure that only one route exists between any two stations on the network.

The ZyAIR uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allow faster 
convergence of the spanning tree (while also being backwards compatible with STP-only 
aware bridges). Using RSTP topology change information does not have to propagate to the 
root bridge and unwanted learned addresses are flushed from the filtering database. In RSTP, 
the port states are Discarding, Learning, and Forwarding.

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 - see the following table.

96, 0 

a

besteffort

64, 32

background

a. The ZyAIR also uses best effort for any DSCP value for which another 

WMM QoS priority is not specified (255, 158 or 37 for example). 

Table 11   ToS and IEEE 802.1d to WMM QoS Priority Level Mapping

Table 12   STP Path Costs

Path Cost

4Mbps

250

100 to 1000

1 to 65535

Path Cost

10Mbps

100

50 to 600

1 to 65535

Path Cost

16Mbps

62

40 to 400

1 to 65535

Path Cost

100Mbps

19

10 to 60

1 to 65535

Path Cost

1Gbps

4

3 to 10

1 to 65535

Path Cost

10Gbps

2

1 to 5

1 to 65535