EnGenius EGS7228P User Manual download pdf (Page 43)

Root Bridge

The Root Bridge serves as an administrative point

for all Spanning Tree calculations to determine which

redundant links to block in order to prevent network

loops. From here, you can view all the information

regarding the Root Bridge within the STP.

All other decisions in a spanning tree network, such as

ports being blocked and ports being put in a forwarding

mode, are made regarding a root bridge. The root bridge

is the “root” of the constructed “tree” within a spanning

tree network. Thus, the root bridge is the bridge with

the lowest bridge ID in the spanning tree network.

The bridge ID includes two parts; the bridge priority (2

bytes)andthebridgeMACaddress(6bytes).The802.1d

defaultbridgepriorityis:32768.STPdevicesexchange

Bridge Protocol Data Units (BPDUs) periodically. 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predenedinterval(called

the Maximum Age), the bridge assumes that the link

to the root bridge is down. The bridge then initiates

negotiationswithotherbridgestorecongurethe

network to re-establish a valid network topology.

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EnGenius EGS7228P User Manual Page 43