ZyXEL Communications GS-2750 User Manual
Page 112
Chapter 11 Spanning Tree Protocol
GS-2750 User’s Guide
112
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
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.
Table 27 Advanced Application > Spanning Tree Protocol > RSTP (continued)
LABEL
DESCRIPTION