Overview; Table 5-1 Ports, Trunk Groups, And Vlans - Nortel Alteon OS 42C4911 Application Manual

Alteon OS Application Guide

Overview

Spanning Tree Group (STG) detects and eliminates logical loops in a bridged or switched net-
work. When multiple paths exist, Spanning Tree configures the network so that a switch uses
only the most efficient path. If that path fails, Spanning Tree automatically sets up another
active path on the network to sustain network operations.
GbESM supports IEEE 802.1d Spanning Tree Protocol. It is compatible with PVST+ by con-
figuring each STP Group in different STP instances.
N – The GbESM also supports IEEE 802.1w Rapid Spanning Tree Protocol, and
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IEEE 802.1s Multiple Spanning Tree Protocol. For more information, see Chapter 6,
"Rapid Spanning Tree Protocol/Multiple Spanning Tree Protocol."
The relationship between port, trunk groups, VLANs, and Spanning Trees is shown in
Table

Table 5-1 Ports, Trunk Groups, and VLANs

Switch Element
Port
Trunk group
VLAN (non-default)
N – Due to Spanning Tree's sequence of listening, learning, and forwarding or blocking,
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lengthy delays may occur.
You can use Port Fast Forwarding (/cfg/port x/fastfwd/ena) to permit a port that
participates in Spanning Tree to bypass the Listening and Learning states and enter directly
into the Forwarding state. While in the Forwarding state, the port listens to the BPDUs to learn
if there is a loop and, if dictated by normal STG behavior (following priorities, and so on), the
port transitions into the Blocking state. This feature permits the GbE Switch Module to inter-
operate well within Rapid Spanning Tree networks.
106 Chapter 5: Spanning Tree Group
5-1.
Belongs to
Trunk group
or
One or more VLANs
One or more VLANs
One Spanning Tree group
42C4911, January 2007