PLANET GSW-1602SF - Manual (Page 80)

User’s Manual of GSW-1602SF / GSW-2404SF
4.7 Rapid Spanning Tree
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 Managed Industrial Switch include these
versions:
„ STP – Spanning Tree Protocol (IEEE 802.1D)
„ RSTP – Rapid Spanning Tree Protocol (IEEE 802.1w)
Spanning Tree Protocol (STP) provides tree topography for any arrangement of bridges. STP also provides one path
between end stations on a network, eliminating loops.
Rapid Spanning Tree Protocol (RSTP) - While Classic Spanning Tree guarantees preventing L2 forwarding loops in a
general network topology, convergence can take up to 30-60 seconds. The convergence time is considered too long for
many applications. When network topology allows, faster convergence may be possible. The Rapid Spanning Tree
Protocol (RSTP) detects and uses of network topologies that provide faster convergence of the spanning tree, without
creating forwarding loops.
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.
-74-