Configuring Standard Stp Parameters - Foundry Networks Switch and Router Installation And Configuration Manual

The Spanning Tree Protocol (STP) eliminates Layer 2 loops in networks, by selectively blocking some ports and
allowing other ports to forward traffic, based on global (bridge) and local (port) parameters you can configure.
This chapter describes how to configure Spanning Tree Protocol (STP) parameters on Foundry Layer 2 Switches
and Layer 3 Switches. Configuration procedures are provided for the standard STP bridge and port parameters
as well as Foundry IronSpan parameters.
IronSpan is a set of Layer 2 features that enable you to overcome limitations in the standard 802.1d Spanning
Tree Protocol (STP). IronSpan includes the following features:
• Fast Port Span
• Fast Uplink Span
• Single-instance STP
• Per VLAN Spanning Tree+ (PVST+) Compatibility
These enhancements extend the operation of standard STP. IronSpan enables you to fine tune standard STP and
avoid some of its limitations.
• To configure standard STP parameters, see "Configuring Standard STP Parameters".
• To configure IronSpan parameters, see "Configuring IronSpan Features" on page 12-16.

Configuring Standard STP Parameters

Foundry Layer 2 and Layer 3 Switches support standard STP as described in the IEEE 802.1D specification. STP
is enabled by default on Layer 2 Switches but disabled by default on Layer 3 Switches.
By default, each port-based VLAN on a Foundry device runs a separate spanning tree (a separate instance of
STP). A Foundry device has one port-based VLAN (VLAN 1) by default that contains all the device's ports. Thus,
by default each Foundry device has one spanning tree. However, if you configure additional port-based VLANs on
a Foundry device, then each of those VLANs and VLAN 1 all run separate spanning trees.
When you configure a port-based VLAN, that VLAN inherits the STP state of the default port-based VLAN. Thus,
if STP is enabled on the default VLAN, STP is also enabled on the new port-based VLAN. You can change the
STP state of the VLAN afterwards. Changes to the STP state of the default VLAN do not affect existing VLANs. A
change to the STP state affects only the VLANs you create after the change.
December 2000
Configuring Spanning Tree Protocol (STP)
Chapter 12
and IronSpan
12 - 1