6 spanning tree protocol, 1 theory, Panning – Interlogix NS3500-28T-4S User Manual User Manual

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4.6 Spanning Tree Protocol

4.6.1 Theory

The Spanning Tree Protocol 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 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. The spanning tree algorithms supported by this switch include these versions:

STP – Spanning Tree Protocol (IEEE 802.1D)

RSTP – Rapid Spanning Tree Protocol (IEEE 802.1w)

MSTP – Multiple Spanning Tree Protocol (IEEE 802.1s)

The IEEE 802.1D Spanning Tree Protocol and IEEE 802.1w Rapid Spanning Tree Protocol allow for the blocking of

links between switches that form loops within the network. When multiple links between switches are detected, a

primary link is established. Duplicated links are blocked from use and become standby links. The protocol allows for

the duplicate links to be used in the event of a failure of the primary link. Once the Spanning Tree Protocol is

configured and enabled, primary links are established and duplicated links are blocked automatically. The reactivation

of the blocked links (at the time of a primary link failure) is also accomplished automatically without operator

intervention.

This automatic network reconfiguration provides maximum uptime to network users. However, the concepts of the

Spanning Tree Algorithm and protocol are a complicated and complex subject and must be fully researched and

understood. It is possible to cause serious degradation of the performance of the network if the Spanning Tree is

incorrectly configured. Please read the following before making any changes from the default values.

The Switch STP performs the following functions:

Creates a single spanning tree from any combination of switching or bridging elements.

Creates multiple spanning trees – from any combination of ports contained within a single switch, in user

specified groups.

Automatically reconfigures the spanning tree to compensate for the failure, addition, or removal of any

element in the tree.

Reconfigures the spanning tree without operator intervention.

Bridge Protocol Data Units

For STP to arrive at a stable network topology, the following information is used:

The unique switch identifier

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