Stp Overview; Configuring Standard Stp Parameters; Stp Parameters And Defaults; Stp Parameters And Defaults - Foundry Networks FESX Manual

Foundry Configuration Guide for the FESX, FSX, and FWSX

STP Overview

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.
You can enable or disable STP on a global basis (for the entire device), a port-based VLAN basis (for the
individual Layer 2 broadcast domain), or an individual port basis.
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 features listed in Table 7.1.

Configuring Standard STP Parameters

Foundry Layer 2 Switches 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 on which STP is enabled and VLAN 1 all run separate spanning
trees.
If you configure a port-based VLAN on the device, the VLAN has the same STP state as the default STP state on
the device. Thus, on Layer 2 Switches, new VLANs have STP enabled by default. On Layer 3 Switches, new
VLANs have STP disabled by default. You can enable or disable STP in each VLAN separately. In addition, you
can enable or disable STP on individual ports.

STP Parameters and Defaults

Table 7.2 lists the default STP states for Foundry devices.
Device Type
Layer 2 Switch
Layer 3 Switch
a.When you create a port-based VLAN, the new VLAN's STP state is the same
as the default STP state on the device. The new VLAN does not inherit the STP
state of the default VLAN.
b.MSTP stands for "Multiple Spanning Tree Protocol". In this type of STP, each
port-based VLAN, including the default VLAN, has its own spanning tree.
References in this documentation to "STP" apply to MSTP. The Single Spanning
Tree Protocol (SSTP) is another type of STP. SSTP includes all VLANs on which
STP is enabled in a single spanning tree. See "Single Spanning Tree (SSTP)" on
page 7-56.
7 - 2
Table 7.2: Default STP States
Default STP Type Default STP State
Enabled
b
MSTP
MSTP Disabled
© Foundry Networks, Inc.
Default STP State
a
of New VLANs
Enabled
Disabled
December 2005