ZyXEL Communications ES-2108 User Manual

ES-2108 Series User’s Guide

Chapter 11 Spanning Tree Protocol

91

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. 

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 a 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 

assigned according to the speed of the bridge. The slower the media, the higher 

the cost - see 

 for more information.

Apply

Click Apply to save your changes back to the switch.

Cancel

Click Cancel to begin configuring this screen afresh.

Table 23   Spanning Tree Protocol: Configuration  (continued)