Allied Telesis AT-S24 - Manual (Page 155)

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Appendix B
Spanning Tree Protocol Concepts
This appendix provides a brief explanation of the STP as implemented
by Allied Telesyn on the switches.
For detailed information on the operation of the STP, consult Section 4
of IEEE Std 802.1D, ISO/IEC 10038: 1993.
The Fast Ethernet switches and the AT-S24 software implement the IEEE
802.1D STP. The STP provides a network with robustness and allows
network administrators to easily change their network topology. Its
implementation reduces complex network topologies (networks with
multiple paths between source and destination nodes) to a single active
topology. This technique guarantees that loops do not occur between
source and destination nodes of the network. Loops are eliminated by
placing some of the redundant ports in a “blocking” state, in which they
do not forward packets but continue to execute the protocol. If the
network topology changes, for example by the failure, removal, or
addition of an active network node, a “blocked” port may be included in
the new active topology and begin forwarding frames.