User's Manual

Chapter 3 | System Settings
Bridge STP Configuration
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◆ Memory Status — Displays detailed information on the current memory
utilization.
Bridge STP Configuration
The Bridge menu enables configuration of the Spanning Tree Protocol (STP) and
the address table aging time.
Spanning Tree
Protocol (STP)
The Spanning Tree Protocol (STP) can be used to detect and disable network loops,
and to provide backup links between switches, bridges or routers. This allows the
wireless bridge to interact with other bridging devices (that is, an STP-compliant
switch, bridge or router) in your network to ensure that only one route exists
between any two stations on the network, and provide backup links which
automatically take over when a primary link goes down.
STP uses a distributed algorithm to select a bridging device (STP-compliant switch,
bridge or router) that serves as the root of the spanning tree network. It selects a
root port on each bridging device (except for the root device) which incurs the
lowest path cost when forwarding a packet from that device to the root device.
Then it selects a designated bridging device from each LAN which incurs the lowest
path cost when forwarding a packet from that LAN to the root device. All ports
connected to designated bridging devices are assigned as designated ports. After
determining the lowest cost spanning tree, it enables all root ports and designated
ports, and disables all other ports. Network packets are therefore only forwarded
between root ports and designated ports, eliminating any possible network loops.
Once a stable network topology has been established, all bridges listen for Hello
BPDUs (Bridge Protocol Data Units) transmitted from the root bridge. If a bridge
does not get a Hello BPDU after a predefined interval (Maximum Age), the bridge
assumes that the link to the root bridge is down. This bridge will then initiate
negotiations with other bridges to reconfigure the network to reestablish a valid
network topology.