ZyXEL xgs-4528f Guia Do Utilizador

Chapter 13 Spanning Tree Protocol

XGS-4528F User’s Guide

Bridge Priority

Bridge priority is used in determining the root switch, root port and 
designated port. The switch with the highest priority (lowest numeric 
value) becomes the STP root switch. If all switches have the same 
priority, the switch with the lowest MAC address will then become the 
root switch. Select a value from the drop-down list box. 

The lower the numeric value you assign, the higher the priority for this 
bridge.

Bridge Priority determines the root bridge, which in turn determines 
Hello Time, Max Age and Forwarding Delay.

Hello Time 

This is the time interval in seconds between BPDU (Bridge Protocol Data 
Units) configuration message generations by the root switch. The 
allowed range is 1 to 10 seconds.

Max Age 

This is the maximum time (in seconds) a switch can wait without 
receiving a BPDU before attempting to reconfigure. All switch ports 
(except for designated ports) should receive BPDUs at regular intervals. 
Any port that ages out STP information (provided in the last BPDU) 
becomes the designated port for the attached LAN. If it is a root port, a 
new root port is selected from among the Switch ports attached to the 
network. The allowed range is 6 to 40 seconds.

Forwarding 
Delay 

This is the maximum time (in seconds) a switch will wait before 
changing states. This delay is required because every switch must 
receive information about topology changes before it starts to forward 
frames. In addition, each port needs time to listen for conflicting 
information that would make it return to a blocking state; otherwise, 
temporary data loops might result. The allowed range is 4 to 30 
seconds.

As a general rule:

Note: 2 * (Forward Delay - 1) >= Max Age >= 2 * (Hello Time + 1)

Port

This field displays the port number. 

*

Settings in this row apply to all ports.

Use this row only if you want to make some settings the same for all 
ports. Use this row first to set the common settings and then make 
adjustments on a port-by-port basis. 

Note: Changes in this row are copied to all the ports as soon as you 

make them.

Active

Select this check box to activate STP on this port. 

Priority

Configure the priority for each port here.

Priority decides which port should be disabled when more than one port 
forms a loop in the Switch. Ports with a higher priority numeric value 
are disabled first. The allowed range is between 0 and 255 and the 
default value is 128.

Path Cost 

Path cost is the cost of transmitting a frame on to a LAN through that 
port. It is recommended that you assign this value according to the 
speed of the bridge. The slower the media, the higher the cost - see 

 for more information.

Table 32   Advanced Application > Spanning Tree Protocol > MRSTP  (continued)