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Configuring Spanning Tree Protocol
IEEE 802.1D Spanning Tree Protocol (STP) allows for the blocking of links between
switches to avoid loops within the network. When multiple links between the 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 STP is configured and enabled, primary links are established and
duplicated links are blocked and put into standby automatically. The reactivation of the
blocked links (at the time of a primary link failure) is also accomplished automatically,
without operator intervention.
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.
The communication between switches via BPDUs results in the following:
•
One switch is elected as the root switch.
•
The shortest distance to the root switch is calculated for each switch.
•
A designated switch is selected. This is the switch closest to the root switch through
which packets will be forwarded to the root.
•
A port for each switch is selected. This is the port providing the best path from the switch
to the root switch.
•
Ports included in the STP are selected.
Spanning Tree Protocol (STP) can be enabled or disabled at the switch level. Only one
spanning tree domain per switch module is supported. You can configure ports to participate
in that spanning tree domain, by enabling or disabling the STP function on a per port basis.
Ports can also be configured in STP bypass mode (fast forward mode) that allows the port to
skip the initial STP states (listening and learning) before enabling it in the forwarding state.
IMPORTANT: The interconnect switch supports mono-Spanning Tree Protocol. Multiple Spanning Tree
domains are not supported.
NOTE: Refer to Appendix D in the HP ProLiant BL e-Class C-GbE Interconnect Switch User Guide for
more information on Spanning Tree Protocol.
HP ProLiant BL e-Class C-GbE Interconnect Switch Menu-driven Interface Reference Guide
HP CONFIDENTIAL Codename: DeLorean Part Number: 322858-001 Last Saved On: 2/4/03 11:56 AM
Configuring the Switch Modules using the Menu-driven Interface
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