Spanning Tree Protocol; Theory - Planet GS-5220 Series User Manual

4.7 Spanning Tree Protocol

4.7.1 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.
User's Manual of GS-5220 LCD Series
223