ZyXEL Communications XGS2220 Series User Manual page 347

The following table describes the labels in this screen.
Table 185 SWITCHING > Spanning Tree Protocol > RSTP
LABEL DESCRIPTION
Active Enable the switch button to activate RSTP. Disable the switch to disable RSTP.
Note: You must also activate Rapid Spanning Tree (RSTP) in the SWITCHING >
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) the 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) the 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:
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.
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
Root Guard Select this check box to enable root guard on this port in order to prevent the switches
attached to the port from becoming the root bridge.
With root guard enabled, a port is blocked when the Switch receives a superior BPDU on it. The
Switch allows traffic to pass through this port again when the switch connected to the port
stops to send superior BPDUs.
Chapter 53 Spanning Tree Protocol
Spanning Tree Protocol > Spanning Tree Setup screen to enable RSTP on the
Switch.
Protocol Data Unit (BPDU).
XGS2220 Series User's Guide
347