Cisco DCNM Layer 2 Switching Configuration Guide, Release 4.2
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This preface describes the audience, organization, and conventions of the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 4.2Cisco DCNM Layer 2 Switching Configuration Guide, Release 4.2. It also provides information on how to obtain related documentation.


This publication is for experienced network administrators who configure and maintain Cisco NX-OS devices.

Document Organization

This document is organized into the following chapters:

Chapter Description

New and Changed Information

Provides release-specific information for each new and changed feature.

Overview of Layer 2

Provides brief descriptions of each feature.

Configuring VLANs

Provides details on configuring VLANs.

Configuring Private VLANs

Provides information on configuring private VLANs.

Configuring Rapid PVST+

Provides information on IEEE 802.1D STP and complete details for configuring Rapid PVST+.

Configuring MST

Provides complete information on configuring MST.

Configuring STP Extensions

Provides details on configuring the Cisco-proprietary STP extensions Bridge Assurance, BPDU Guard, BPDU Filtering, Loop Guard, Root Guard, and PVST Simulation.

Configuring Link-State Tracking

Provides information on configuring LST for redundancy.

Configuration Limits for Cisco NX-OS Layer 2 Switching Features

Provides information on limits for Layer 2 switching features.

Document Conventions

Command descriptions use the following conventions:

Convention Description

Bold text indicates the commands and keywords that you enter literally as shown.


Italic text indicates arguments for which the user supplies the values.


Square brackets enclose an optional element(keyword or argument).

[x | y]

Square brackets enclosing keywords or arguments separated by a vertical bar indicate an optional choice.

{x | y}

Braces enclosing keywords or arguments separated by a vertical bar indicate a required choice.

[x {y | z}]

Nested set of square brackets or braces indicate optional or required choices within optional or required elements. Braces and a vertical bar within square brackets indicate a required choice within an optional element.


Indicates a variable for which you supply values, in context where italics cannot be used.

string A nonquoted set of characters. Do not use quotation marks around the string or the string will include the quotation marks.

Screen examples use the following conventions:

Convention Description
screen font

Terminal sessions and information the switch displays are in screen font.

boldface screen font

Information you must enter is in boldface screen font.

italic screen font

Arguments for which you supply values are in italic screen font.

< >

Nonprinting characters, such as passwords, are in angle brackets.

[ ]

Default responses to system prompts are in square brackets.

!, #

An exclamation point (!) or a pound sign (#) at the beginning of a line of code indicates a comment line.

This document uses the following conventions:


Means reader take note. Notes contain helpful suggestions or references to material not covered in the manual.


Means reader be careful. In this situation, you might do something that could result in equipment damage or loss of data.

Obtaining Documentation and Submitting a Service Request

For information on obtaining documentation, submitting a service request, and gathering additional information, see the monthly What's New in Cisco Product Documentation, which also lists all new and revised Cisco technical documentation, at:

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