Chapter 11 Spanning Tree Protocol

 

Table 23 Advanced Application > Spanning Tree Protocol > RSTP (continued)

 

LABEL

DESCRIPTION

 

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 RSTP 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

 

 

recommended to assign this value according to the speed of the bridge. The

 

 

slower the media, the higher the cost - see Table 21 on page 96 for more

 

 

information.

 

 

 

 

Apply

Click Apply to save your changes to the Switch’s run-time memory. The Switch

 

 

loses these changes if it is turned off or loses power, so use the Save link on the

 

 

top navigation panel to save your changes to the non-volatile memory when you

 

 

are done configuring.

 

 

 

 

Cancel

Click Cancel to begin configuring this screen afresh.

 

 

 

 

101

ES-2024 Series User’s Guide