Interlogix GE-DSH-73 Series User Manual - Manual (Page 93)

Chapter 5: Web-Based Management
GE-DSH-73/DSH-82 and DSH-82-PoE User Manual 89
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
• The path cost to the root associated with each switch port
• The port identifier
STP communicates between switches on the network using Bridge Protocol Data
Units (BPDUs). Each BPDU contains the following information:
• The unique identifier of the switch that the transmitting switch currently believes
is the root switch.
• The path cost to the root from the transmitting port.
• The port identifier of the transmitting port.
The switch sends BPDUs to communicate and construct the spanning-tree topology.
All switches connected to the LAN on which the packet is transmitted will receive the
BPDU. BPDUs are not directly forwarded by the switch, but the receiving switch uses
the information in the frame to calculate a BPDU, and, if the topology changes,
initiates a BPDU transmission.