Configuring Spanning Tree; Spanning Tree Overview - Avaya G350 Administration

Configuring advanced switching

Configuring spanning tree

Configuring spanning tree
This section provides information about configuring spanning tree on the G350 and contains the
following topics:
•

Spanning tree overview

•
Spanning tree CLI commands
spanning tree protocol on the G350
•
Spanning tree configuration examples
Spanning tree overview
G350 devices support both common Spanning Tree protocol (802.1d) and the enhanced Rapid Spanning
Tree protocol (802.1w). The 802.1w standard is a faster and more sophisticated version of the 802.1d
(STP) standard. Spanning Tree makes it possible to recover connectivity after an outage within a minute
or so. RSTP, with its "rapid" algorithm, can restore connectivity to a network where a backbone link has
failed in much less time.
Spanning tree protocol
The Spanning Tree Algorithm ensures the existence of a loop-free topology in networks that contain
parallel bridges. A loop occurs when there are alternate routes between hosts. If there is a loop in an
extended network, bridges may forward traffic indefinitely, which can result in increased traffic and
degradation in network performance.
The Spanning Tree Algorithm:
•
Produces a logical tree topology out of any arrangement of bridges. The result is a single path
between any two end stations on an extended network.
•
Provides a high degree of fault tolerance. It allows the network to automatically reconfigure the
spanning tree topology if there is a bridge or data-path failure.
The Spanning Tree Algorithm requires five values to derive the spanning tree topology. These are:
•
A multicast address specifying all bridges on the extended network. This address is
media-dependent and is automatically determined by the software.
•
A network-unique identifier for each bridge on the extended network.
•
A unique identifier for each bridge/LAN interface (a port).
•
The relative priority of each port.
•
The cost of each port.
After these values are assigned, bridges multicast and process the formatted frames (called Bridge
Protocol Data Units, or BPDUs) to derive a single, loop-free topology throughout the extended network.
The bridges exchange BPDU frames quickly, minimizing the time that service is unavailable between
hosts.
118
— an overview of spanning tree protocol
— a list and description of CLI commands used to configure
— examples of spanning tree protocol configurations
Administration of the Avaya G350 Media Gateway
June 2004