Blade ICE G8000 manual 1Ports, Trunk Groups, and VLANs

RackSwitch G8000 Application Guide

Overview

Spanning Tree Protocol detects and eliminates logical loops in a bridged or switched network. 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.

The G8000 supports the following Spanning Tree Protocols:

„IEEE 802.1D (2004) Rapid Spanning Tree Protocol (RSTP). RSTP enhances the Spanning Tree Protocol to provide rapid convergence on Spanning Tree Group 1.

„IEEE 802.1Q (2003) Multiple Spanning Tree Protocol, which extends RSTP to multiple Spanning Tree Groups. MSTP provides both rapid convergence and load balancing in a VLAN environment, using multiple VLANs in each Spanning-Tree Group (STG).

„Per VLAN Rapid Spanning Tree Plus Protocol (PVRST+), which enhances the RSTP protocol by adding the ability to have multiple spanning tree groups. PVRST+ is based on IEEE 802.1w Rapid Spanning Tree Protocol.

The relationship between port, trunk groups, VLANs, and Spanning Trees is shown in Table 5-1.

Table 5-1Ports, Trunk Groups, and VLANs

Switch Element	Belongs to
Port	Trunk group
	or
	One or more VLANs
Trunk group	One or more VLANs
VLAN (non-default)	RSTP: One VLAN per Spanning Tree group
	PVRST+: One VLAN per Spanning Tree Group
	MSTP: Multiple VLANs per Spanning Tree group

NOTE – Due to Spanning Tree’s sequence of discarding, learning, and forwarding, lengthy delays may occur.

You can use a port’s spanning-tree edge command to permit a port that participates in Spanning Tree to bypass the Discarding and Learning states, and enter directly into the Forwarding state.

74 „ Chapter 5: Spanning Tree BMD00041, November 2008