User`s manual

NPort 6000 Series User’s Manual Module Settings
6-5
STP Configuration
After all the bridges on the network agree on the identity of the Root Bridge, and all other relevant
parameters have been established, each bridge is configured to forward traffic only between its
Root Port and the Designated Bridge Ports for the respective network segments. All other ports are
blocked, which means that they will not be allowed to receive or forward traffic.
STP Reconfiguration
Once the network topology has stabilized, each bridge listens for Hello BPDUs transmitted from
the Root Bridge at regular intervals. If a bridge does not receive a Hello BPDU after a certain
interval (the Max Age time), the bridge assumes that the Root Bridge, or a link between itself and
the Root Bridge, has gone down. This will trigger the bridge to reconfigure the network to account
for the change.
Differences between RSTP and STP
RSTP is similar to STP, but includes additional information in the BPDUs that allow each bridge
to confirm that it has taken action to prevent loops from forming when it decides to enable a link to
a neighboring bridge. Adjacent bridges connected via point-to-point links will be able to enable a
link without waiting to ensure that all other bridges in the network have had time to react to the
change. The main benefit of RSTP is that the configuration decision is made locally rather than
network-wide, allowing RSTP to carry out automatic configuration and restore a link faster than
STP.
Configuring RSTP
The following figures indicate which Rapid Spanning Tree Protocol parameters can be configured.
A more detailed explanation of each parameter follows.
Redundancy protocol: RSTP (IEEE 802.1W/1D) is the only redundancy protocol option.
Bridge priority: Increase this device’s bridge priority by selecting a lower number. A device with
a higher bridge priority has a greater chance of being established as the root of the Spanning Tree
topology. The factory default is 32768.
Hello time (sec.): The root of the Spanning Tree topology periodically sends out a “hello”
message to other devices on the network to check if the topology is healthy. The “hello time” is the
amount of time the root waits between sending hello messages. The factory default is 2.(sec)