Operation Manual

41
Once a stable network topology has been established,
all bridges listen for Hello Bridge Protocol Data Units
(BPDUs) transmitted from the Root Bridge of the
Spanning Tree. If a bridge does not receive a Hello BPDU
afterapredenedinterval(knownastheMaximumAge),
the bridge will assume that the link to the Root Bridge
is down and unavailable. This bridge then initiates
negotiationswithotherbridgestorecongurethe
network to reestablish a valid network topology.
Global Settings
Spanning Tree Protocol (STP) is a Layer 2 protocol that
runs on Switches. Spanning Tree Protocol (STP) allows
you to ensure that you do not create loops when you
have redundant paths in the network. STP provides a
single active path between two devices on a network
in order to prevents loops from being formed when the
Switch is interconnected via multiple paths.
STP uses a distributed algorithm to select a bridging
device that serves as the root for the spanning tree
network. It does this by selecting a root port on each
bridging device to incur the lowest path cost when
forwarding a packet from that device to the root device.
It then 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. Next, 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, disabling all other ports. Network packets are
therefore only forwarded between root ports and
designated ports, eliminating any possible network
loops. STP provides a single active path between two
devices on a network in order to prevent loops from
being formed when the Switch is interconnected via
multiple paths.