47
Table of Contents
Linksys
47
Table of Contents
Linksys
Chapter 7 Spanning Tree
Management
Spanning Tree Management
This section describes the Spanning Tree Protocol (STP) (IEEE802.1D, IEEE802.1s
and IEEE802.1w) and covers the following topics:
• Overview
• Spanning Tree
• STP Interfaces
• RSTP Interfaces
• MSTP Properties
• VLAN to MSTP
• MSTP Instance Status
• MSTP Instance Interface
Overview
STP protects a Layer 2 broadcast domain from broadcast storms by selectively
setting links to standby mode to prevent loops. In standby mode, these links
temporarily stop transferring user data. After the topology changes so that
the data transfer is made possible, the links are automatically re-activated.
Loops occur when alternate routes exist between hosts. Loops in an extended
network can cause switches to forward traffic indefinitely, resulting in
increased traffic load and reduced network efficiency.
STP provides a tree topology for any arrangement of switches and
interconnecting links, by creating a unique path between end stations on a
network, and thereby eliminating loops.
The device supports the following Spanning Tree Protocol versions:
• Classic STP – Provides a single path between any two end stations,
avoiding and eliminating loops.
• Rapid STP (RSTP) – Detects network topologies to provide faster
convergence of the spanning tree. This is most effective when the
network topology is naturally tree-structured, and therefore faster
convergence might be possible. RSTP is enabled by default.
Spanning Tree
The Spanning Tree page contains parameters for enabling STP or RSTP. Use
the STP Interface page and RSTP Interface page to configure ports with these
modes, respectively.
To set the STP status and global settings, do the following:
STEP 1 Click Configuration > Spanning Tree Management > Spanning Tree.
STEP 2 Enter the parameters.
Global Settings
• Spanning Tree—Select to enable STP on the device.
• Spanning Tree Mode—Select an STP mode—Classic STP or Rapid STP.
• Path Cost Default Values—Selects the method used to assign default path
costs to the STP ports. The default path cost assigned to an interface varies
according to the selected method.
• Short—Specifies the range 1 through 65,535 for port path costs.
• Long—Specifies the range 1 through 200,000,000 for port path costs.
• BPDU Handling—Select how Bridge Protocol Data Unit (BPDU) packets are
managed when STP is disabled on the port or the device. BPDUs are used
to transmit spanning tree information.
• Filtering—Filters BPDU packets when Spanning Tree is disabled on an
interface.
• Flooding—Floods BPDU packets when Spanning Tree is disabled on an
interface.
Bridge Configuration
• Priority—Set the global priority value. The priority value influences the
port choice when a bridge has two ports connected in a loop. The priority
is a value from 0 to 240, set in increments of 16.
• Hello Time—Set the interval (in seconds) that a root bridge waits
between configuration messages.
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