Installation guide

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10 SPANNING TREE
This chapter includes the following sections for configuring Spanning Tree:
◆ “Configuring the Spanning Tree Protocol” on page 71
◆ “Configuring STP Global Settings” on page 72
◆ “Configuring STP Port Settings” on page 75
CONFIGURING THE SPANNING TREE PROTOCOL
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 switch 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.
This switch supports Rapid Spanning Tree Protocol (RSTP), but is backward
compatible with Spanning Tree Protocol (STP).
◆ STP - 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.