ZyXEL Communications MES3500-24 User Manual

Chapter 13 Spanning Tree Protocol

MES3500-24/24F User’s Guide

Active

Select this check box to activate an STP tree. Clear this checkbox to disable an STP tree.

Note: You must also activate Multiple Rapid Spanning Tree in the Advanced Application 

> Spanning Tree Protocol > Configuration screen to enable MRSTP on the 
Switch.

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. 

Edge

Select this check box to configure a port as an edge port when it is directly attached to a 
computer. An edge port changes its initial STP port state from blocking state to forwarding 
state immediately without going through listening and learning states right after the port 
is configured as an edge port or when its link status changes.

Note: An edge port becomes a non-edge port as soon as it receives a Bridge Protocol Data 

Unit (BPDU).

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.

Tree

Select which STP tree configuration this port should participate in.

Advanced Application > Spanning Tree Protocol > MRSTP  (continued)