First Published: February 29, 2012
Last Modified: March 22, 2012
Americas Headquarters
Cisco Systems, Inc. 170 West Tasman Drive
San Jose, CA 95134-1706 USA http://www.cisco.com Tel: 408 526-4000
800 553-NETS (6387) Fax: 408 527-0883
Text Part Number: OL-26590-01
THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL STATEMENTS, INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.
THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE INFORMATION PACKET THAT SHIPPED WITH THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE. IF YOU ARE UNABLE TO LOCATE THE SOFTWARE LICENSE OR LIMITED WARRANTY, CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY.
The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California, Berkeley (UCB) as part of UCB's public domain version of the UNIX operating system. All rights reserved. Copyright © 1981, Regents of the University of California.
NOTWITHSTANDING ANY OTHER WARRANTY HEREIN, ALL DOCUMENT FILES AND SOFTWARE OF THESE SUPPLIERS ARE PROVIDED “AS IS" WITH ALL FAULTS. CISCO AND THE ABOVE-NAMED SUPPLIERS DISCLAIM ALL WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, THOSE OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OR ARISING FROM A COURSE OF DEALING, USAGE, OR TRADE PRACTICE.
IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES, INCLUDING, WITHOUT LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: http:// www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© Cisco Systems, Inc. All rights reserved.
C O N T E N T S
P r e f a c e
C H A P T E R 1
C H A P T E R 2
C H A P T E R 3
Preface xi
Audience xi
Document Conventions xi
Related Documentation for Nexus 3000 Series NX-OS Software xii
Obtaining Documentation and Submitting a Service Request xiv
New and Changed Information for this Release 1
New and Changed Information for this Release 1 |
|
|||
Overview 3 |
|
|
|
|
Layer 2 Ethernet Switching Overview |
3 |
|
||
VLANs 3 |
|
|
|
|
Private VLANs |
4 |
|
|
|
Spanning Tree |
4 |
|
|
|
STP Overview |
4 |
|
|
|
Rapid PVST+ |
5 |
|
|
|
MST 5 |
|
|
|
|
STP Extensions 5 |
|
|
||
Configuring Ethernet Interfaces 7 |
|
|
||
Information About Ethernet Interfaces |
7 |
|
||
About the Interface Command 7 |
|
|
||
About the Unidirectional Link Detection Parameter |
8 |
|||
Default UDLD Configuration |
9 |
|
||
UDLD Aggressive and Nonaggressive Modes |
9 |
|||
About Interface Speed 10 |
|
|
||
About the Cisco Discovery Protocol |
10 |
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
iii |
Contents
C H A P T E R 4
Default CDP Configuration |
10 |
|
|
|||
About the Error-Disabled State 10 |
|
|
||||
About Port Profiles 11 |
|
|
|
|
|
|
Guidelines and Limitations for Port Profiles 11 |
||||||
About the Debounce Timer Parameters |
11 |
|
||||
About MTU Configuration |
11 |
|
|
|
|
|
Configuring Ethernet Interfaces |
11 |
|
|
|
||
Configuring the UDLD Mode |
12 |
|
|
|
||
Changing an Interface Port Mode |
13 |
|
|
|||
Configuring Interface Speed |
14 |
|
|
|
||
Disabling Link Negotiation |
15 |
|
|
|
||
Configuring the CDP Characteristics 16 |
|
|||||
Enabling or Disabling CDP |
17 |
|
|
|
||
Enabling the Error-Disabled Detection |
18 |
|
||||
Enabling the Error-Disabled Recovery |
19 |
|
||||
Configuring the Error-Disabled Recovery Interval 19 |
||||||
Configuring the Debounce Timer |
20 |
|
|
|||
Configuring the Description Parameter |
20 |
|
||||
Disabling and Restarting Ethernet Interfaces |
21 |
|||||
Displaying Interface Information |
21 |
|
|
|||
Displaying Input Packet Discard Information 23 |
||||||
Default Physical Ethernet Settings |
24 |
|
|
|||
Configuring VLANs 27 |
|
|
|
|
|
|
Information About VLANs |
27 |
|
|
|
|
|
Understanding VLANs |
27 |
|
|
|
|
|
VLAN Ranges 28 |
|
|
|
|
|
|
Creating, Deleting, and Modifying VLANs |
29 |
|||||
About the VLAN Trunking Protocol 30 |
|
|
||||
Guidelines and Limitations for VTP 30 |
|
|||||
Configuring a VLAN 30 |
|
|
|
|
|
|
Creating and Deleting a VLAN 30 |
|
|
||||
Configuring a VLAN 31 |
|
|
|
|
|
|
Adding Ports to a VLAN 32 |
|
|
|
|
||
Configuring a VLAN as a Routed SVI |
33 |
|
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
iv |
OL-26590-01 |
Contents
Configuring a VLAN as a Management SVI 34
Configuring VTP 34
Verifying VLAN Configuration 36
C H A P T E R 5
C H A P T E R 6
Configuring Private VLANs 37 |
|
|
|
|
|
Information About Private VLANs 37 |
|
|
|
|
|
Primary and Secondary VLANs in Private VLANs |
38 |
|
|
||
Private VLAN Ports 38 |
|
|
|
|
|
Primary, Isolated, and Community Private VLANs |
39 |
|
|
||
Associating Primary and Secondary VLANs |
40 |
|
|
||
Private VLAN Promiscuous Trunks |
41 |
|
|
|
|
Private VLAN Isolated Trunks 41 |
|
|
|
|
|
Broadcast Traffic in Private VLANs |
41 |
|
|
|
|
Private VLAN Port Isolation 41 |
|
|
|
|
|
Guidelines and Limitations for Private VLANs 42 |
|
|
|
||
Configuring a Private VLAN |
42 |
|
|
|
|
Enabling Private VLANs |
42 |
|
|
|
|
Configuring a VLAN as a Private VLAN 43 |
|
|
|
||
Associating Secondary VLANs with a Primary Private VLAN |
43 |
||||
Configuring an Interface as a Private VLAN Host Port |
45 |
|
|||
Configuring an Interface as a Private VLAN Promiscuous Port |
45 |
||||
Configuring a Promiscuous Trunk Port 46 |
|
|
|
||
Configuring an Isolated Trunk Port |
46 |
|
|
|
|
Configuring the Allowed VLANs for PVLAN Trunking Ports |
46 |
||||
Configuring Native 802.1Q VLANs on Private VLANs |
47 |
|
|||
Verifying the Private VLAN Configuration 47 |
|
|
|
Configuring Access and Trunk Interfaces 49
Information About Access and Trunk Interfaces 49
Understanding Access and Trunk Interfaces 49
Understanding IEEE 802.1Q Encapsulation 50
Understanding Access VLANs 51
Understanding the Native VLAN ID for Trunk Ports 52
Understanding Allowed VLANs 52
Understanding Native 802.1Q VLANs 52
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
v |
Contents
|
|
Configuring Access and Trunk Interfaces 53 |
|
|
|
||||
|
|
Configuring a LAN Interface as an Ethernet Access Port |
53 |
||||||
|
|
Configuring Access Host Ports |
54 |
|
|
|
|
||
|
|
Configuring Trunk Ports 54 |
|
|
|
|
|
|
|
|
|
Configuring the Native VLAN for 802.1Q Trunking Ports |
55 |
||||||
|
|
Configuring the Allowed VLANs for Trunking Ports 55 |
|
||||||
|
|
Configuring Native 802.1Q VLANs |
56 |
|
|
|
|||
|
|
Verifying Interface Configuration |
57 |
|
|
|
|
||
|
|
Configuring Switching Modes 59 |
|
|
|
|
|
|
|
C H A P T E R |
7 |
|
|
|
|
|
|
||
|
|
Information About Switching Modes 59 |
|
|
|
||||
|
|
Guidelines and Limitations for Switching Modes |
60 |
|
|||||
|
|
Licensing Requirements for Switching Modes |
60 |
|
|
||||
|
|
Default Settings for Switching Modes |
61 |
|
|
|
|||
|
|
Configuring Switching Modes 61 |
|
|
|
|
|
||
|
|
Enabling Store-and-Forward Switching 61 |
|
|
|
||||
|
|
Reenabling Cut-Through Switching |
61 |
|
|
|
|||
|
|
Feature History for Switching Modes |
62 |
|
|
|
|||
|
|
Configuring Rapid PVST+ |
63 |
|
|
|
|
|
|
C H A P T E R |
8 |
|
|
|
|
|
|
||
|
|
Information About Rapid PVST+ |
63 |
|
|
|
|
||
|
|
Understanding STP |
63 |
|
|
|
|
|
|
|
|
STP Overview |
63 |
|
|
|
|
|
|
|
|
Understanding How a Topology is Created |
64 |
|
|||||
|
|
Understanding the Bridge ID 64 |
|
|
|
||||
|
|
Bridge Priority Value |
|
64 |
|
|
|
|
|
|
|
Extended System ID |
|
65 |
|
|
|
|
|
|
|
STP MAC Address Allocation 65 |
|
|
|
||||
|
|
Understanding BPDUs 66 |
|
|
|
|
|
||
|
|
Election of the Root Bridge 67 |
|
|
|
|
|||
|
|
Creating the Spanning Tree Topology |
67 |
|
|
||||
|
|
Understanding Rapid PVST+ |
68 |
|
|
|
|
||
|
|
Rapid PVST+ Overview |
68 |
|
|
|
|
||
|
|
Rapid PVST+ BPDUs 69 |
|
|
|
|
|
|
|
|
|
Proposal and Agreement Handshake 70 |
|
|
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
vi |
OL-26590-01 |
Contents
C H A P T E R 9
Protocol Timers 71
Port Roles 71
Port States 72
Rapid PVST+ Port State Overview 72
Blocking State 73
Learning State 73
Forwarding State 73
Disabled State 74
Summary of Port States 74
Synchronization of Port Roles 74
Processing Superior BPDU Information 75
Processing Inferior BPDU Information 76
Spanning-Tree Dispute Mechanism 76
Port Cost 76
Port Priority 77
Rapid PVST+ and IEEE 802.1Q Trunks 77
Rapid PVST+ Interoperation with Legacy 802.1D STP 77
Rapid PVST+ Interoperation with 802.1s MST 78
Configuring Rapid PVST+ 78
Enabling Rapid PVST+ 78
Enabling Rapid PVST+ per VLAN 79
Configuring the Root Bridge ID 80
Configuring a Secondary Root Bridge 81
Configuring the Rapid PVST+ Port Priority 82
Configuring the Rapid PVST+ Pathcost Method and Port Cost 83
Configuring the Rapid PVST+ Bridge Priority of a VLAN 83
Configuring the Rapid PVST+ Hello Time for a VLAN 84
Configuring the Rapid PVST+ Forward Delay Time for a VLAN 85
Configuring the Rapid PVST+ Maximum Age Time for a VLAN 85
Specifying the Link Type 85
Restarting the Protocol 86
Verifying Rapid PVST+ Configurations 86
Configuring Multiple Spanning Tree 89
Information About MST 89
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
vii |
Contents
MST Overview 89
MST Regions 90
MST BPDUs 90
MST Configuration Information 91
IST, CIST, and CST 91
IST, CIST, and CST Overview 91
Spanning Tree Operation Within an MST Region 92
Spanning Tree Operations Between MST Regions 92
MST Terminology 93
Hop Count 94
Boundary Ports 94
Spanning-Tree Dispute Mechanism 95
Port Cost and Port Priority 96
Interoperability with IEEE 802.1D 96
Interoperability with Rapid PVST+: Understanding PVST Simulation 97
Configuring MST 97
MST Configuration Guidelines 97
Enabling MST 97
Entering MST Configuration Mode 98
Specifying the MST Name 99
Specifying the MST Configuration Revision Number 100
Specifying the Configuration on an MST Region 100
Mapping and Unmapping VLANs to MST Instances 102
Mapping Secondary VLANs to Same MSTI as Primary VLANs for Private VLANs 102 |
|
Configuring the Root Bridge |
103 |
Configuring a Secondary Root Bridge 104 |
|
Configuring the Port Priority |
105 |
Configuring the Port Cost 106 |
|
Configuring the Switch Priority 106 |
|
Configuring the Hello Time |
107 |
Configuring the Forwarding-Delay Time 108 |
Configuring the Maximum-Aging Time |
108 |
Configuring the Maximum-Hop Count |
109 |
Configuring PVST Simulation Globally |
109 |
Configuring PVST Simulation Per Port |
110 |
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
viii |
OL-26590-01 |
Contents
Specifying the Link Type 111
Restarting the Protocol 111
C H A P T E R 1 0
C H A P T E R 1 1
C H A P T E R 1 2
Verifying MST Configurations 112 |
|
|
|
|
Configuring STP Extensions 113 |
|
|
|
|
About STP Extensions 113 |
|
|
|
|
Information About STP Extensions |
113 |
|
||
Understanding STP Port Types |
113 |
|
||
Spanning Tree Edge Ports |
113 |
|
||
Spanning Tree Network Ports |
114 |
|
||
Spanning Tree Normal Ports |
114 |
|
||
Understanding Bridge Assurance |
114 |
|
||
Understanding BPDU Guard |
114 |
|
|
|
Understanding BPDU Filtering |
115 |
|
||
Understanding Loop Guard |
116 |
|
|
|
Understanding Root Guard 116 |
|
|
|
|
Configuring STP Extensions 117 |
|
|
|
|
STP Extensions Configuration Guidelines 117 |
|
|||
Configuring Spanning Tree Port Types Globally |
117 |
|||
Configuring Spanning Tree Edge Ports on Specified Interfaces 118 |
||||
Configuring Spanning Tree Network Ports on Specified Interfaces 119 |
||||
Enabling BPDU Guard Globally |
120 |
|
||
Enabling BPDU Guard on Specified Interfaces 121 |
||||
Enabling BPDU Filtering Globally 122 |
|
|||
Enabling BPDU Filtering on Specified Interfaces |
123 |
|||
Enabling Loop Guard Globally |
124 |
|
||
Enabling Loop Guard or Root Guard on Specified Interfaces 124 |
||||
Verifying STP Extension Configuration 125 |
|
|||
Configuring LLDP 127 |
|
|
|
|
Configuring Global LLDP Commands |
127 |
|
||
Configuring Interface LLDP Commands |
129 |
|
||
Configuring the MAC Address Table |
131 |
|
|
|
Information About MAC Addresses |
131 |
|
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
ix |
Contents
C H A P T E R 1 3
C H A P T E R 1 4
Configuring MAC Addresses 131
Configuring a Static MAC Address 131
Configuring the Aging Time for the MAC Table 132
Clearing Dynamic Addresses from the MAC Table 133
Verifying the MAC Address Configuration 133
Configuring IGMP Snooping 135
Information About IGMP Snooping 135
IGMPv1 and IGMPv2 136
IGMPv3 137
IGMP Snooping Querier 137
IGMP Forwarding 137
Configuring IGMP Snooping Parameters 138
Verifying IGMP Snooping Configuration 141
Configuring Traffic Storm Control 143
Information About Traffic Storm Control 143
Traffic Storm Guidelines and Limitations 144
Configuring Traffic Storm Control 145
Verifying Traffic Storm Control Configuration 146
Traffic Storm Control Example Configuration 146
Default Traffic Storm Settings 146
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
x |
OL-26590-01 |
This preface contains the following sections:
• |
Audience, page xi |
• |
Document Conventions, page xi |
• |
Related Documentation for Nexus 3000 Series NX-OS Software, page xii |
• |
Obtaining Documentation and Submitting a Service Request, page xiv |
This publication is for experienced network administrators who configure and maintain Cisco Nexus Series devices.
Command descriptions use the following conventions:
Convention |
Description |
bold |
Bold text indicates the commands and keywords that you enter literally |
|
as shown. |
Italic |
Italic text indicates arguments for which the user supplies the values. |
[x] |
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. |
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
xi |
Preface
Convention |
Description |
[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. |
variable |
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. |
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:
Note Means reader take note. Notes contain helpful suggestions or references to material not covered in the manual.
Caution Means reader be careful. In this situation, you might do something that could result in equipment damage or loss of data.
Related Documentation for Nexus 3000 Series NX-OS Software
The entire Cisco NX-OS 3000 Series documentation set is available at the following URL:
http://www.cisco.com/en/US/products/ps11541/tsd_products_support_series_home.html
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
xii |
OL-26590-01 |
Preface
Related Documentation for Nexus 3000 Series NX-OS Software
Release Notes
The release notes are available at the following URL:
http://www.cisco.com/en/US/products/ps11541/prod_release_notes_list.html
Installation and Upgrade Guides
The installation and upgrade guides are available at the following URL:
http://www.cisco.com/en/US/products/ps11541/prod_installation_guides_list.html
The documents in this category include:
•Cisco Nexus 5000 Series, Cisco Nexus 3000 Series, and Cisco Nexus 2000 Series Safety Information and Documentation
•Regulatory, Compliance, and Safety Information for the Cisco Nexus 5000 Series, Cisco Nexus 3000 Series, and Cisco Nexus 2000 Series
•Cisco Nexus 3000 Series Hardware Installation Guide
Configuration Guides
The configuration guides are available at the following URL: http://www.cisco.com/en/US/products/ps11541/products_installation_and_configuration_guides_list.html The documents in this category include:
•Configuration Limits for Cisco NX-OS
•Fundamentals Configuration Guide
•Layer 2 Switching Configuration Guide
•Multicast Configuration Guide
•Quality of Service Configuration Guide
•Security Configuration Guide
•System Management Configuration Guide
•Unicast Routing Configuration Guide
•Verified Scalability Guide for Cisco NX-OS
Technical References
The technical references are available at the following URL:
http://www.cisco.com/en/US/products/ps11541/prod_technical_reference_list.html
Error and System Messages
The error and system message reference guides are available at the following URL:
http://www.cisco.com/en/US/products/ps11541/products_system_message_guides_list.html
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
xiii |
Preface
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:
http://www.cisco.com/en/US/docs/general/whatsnew/whatsnew.html
Subscribe to the What's New in Cisco Product Documentation as a Really Simple Syndication (RSS) feed and set content to be delivered directly to your desktop using a reader application. The RSS feeds are a free service and Cisco currently supports RSS version 2.0.
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
xiv |
OL-26590-01 |
C H A P T E R 1
The following table provides an overview of the significant changes to this guide for this current release. The table does not provide an exhaustive list of all changes made to the configuration guides or of the new features in this release.
• New and Changed Information for this Release, page 1
The following table provides an overview of the significant changes to this guide for this current release. The table does not provide an exhaustive list of all changes made to the configuration guides or of the new features in this release.
Table 1: New and Changed Features
Feature |
Description |
Added or |
Where Documented |
|
|
Changed |
|
|
|
in |
|
|
|
Release |
|
Switching Modes |
Added a new chapter about configuring your |
5.0(3)U3(1) |
ConfiguringSwitching |
|
switching mode. There are two switching |
|
Modes, on page 59 |
|
modes: cut-through and store-and-forward. |
|
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
1 |
New and Changed Information for this Release
New and Changed Information for this Release
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
2 |
OL-26590-01 |
C H A P T E R 2
This chapter contains the following sections:
• |
Layer 2 Ethernet Switching Overview, page 3 |
• |
VLANs, page 3 |
• |
Private VLANs, page 4 |
• |
Spanning Tree , page 4 |
The device supports simultaneous, parallel connections between Layer 2 Ethernet segments. Switched connections between Ethernet segments last only for the duration of the packet. New connections can be made between different segments for the next packet.
The device solves congestion problems caused by high-bandwidth devices and a large number of users by assigning each device (for example, a server) to its own 10-, 100-, 1000-Mbps, or 10-Gigabit collision domain. Because each LAN port connects to a separate Ethernet collision domain, servers in a switched environment achieve full access to the bandwidth.
Because collisions cause significant congestion in Ethernet networks, an effective solution is full-duplex communication. Typically, 10/100-Mbps Ethernet operates in half-duplex mode, which means that stations can either receive or transmit. In full-duplex mode, which is configurable on these interfaces, two stations can transmit and receive at the same time. When packets can flow in both directions simultaneously, the effective Ethernet bandwidth doubles. 1/10-Gigabit Ethernet operates in full-duplex only.
A VLAN is a switched network that is logically segmented by function, project team, or application, without regard to the physical locations of the users. VLANs have the same attributes as physical LANs, but you can group end stations even if they are not physically located on the same LAN segment.
Any switch port can belong to a VLAN, and unicast, broadcast, and multicast packets are forwarded and flooded only to end stations in that VLAN. Each VLAN is considered as a logical network, and packets destined for stations that do not belong to the VLAN must be forwarded through a bridge or a router.
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
3 |
Overview
All ports, including the management port, are assigned to the default VLAN (VLAN1) when the device first comes up. A VLAN interface, or switched virtual interface (SVI), is a Layer 3 interface that is created to provide communication between VLANs.
The devices support 4094 VLANs in accordance with the IEEE 802.1Q standard. These VLANs are organized into several ranges, and you use each range slightly differently. Some of these VLANs are reserved for internal use by the device and are not available for configuration.
Note Inter-Switch Link (ISL) trunking is not supported on the NX-OS software for the Cisco Nexus 3000 Series.
Private VLANs
Private VLANs provide traffic separation and security at the Layer 2 level.
A private VLAN is one or more pairs of a primary VLAN and a secondary VLAN, all with the same primary VLAN. The two types of secondary VLANs are isolated and community VLANs. Hosts on isolated VLANs communicate only with hosts in the primary VLAN. Hosts in a community VLAN can communicate only among themselves and with hosts in the primary VLAN but not with hosts in isolated VLANs or in other community VLANs.
Regardless of the combination of isolated and community secondary VLANs, all interfaces within the primary VLAN comprise one Layer 2 domain, and therefore, require only one IP subnet.
This section discusses the implementation of the Spanning Tree Protocol (STP). Spanning tree is used to refer to IEEE 802.1w and IEEE 802.1s. When the IEEE 802.1D Spanning Tree Protocol is referred to in the publication, 802.1D is stated specifically.
STP provides a loop-free network at the Layer 2 level. Layer 2 LAN ports send and receive STP frames, which are called Bridge Protocol Data Units (BPDUs), at regular intervals. Network devices do not forward these frames but use the frames to construct a loop-free path.
802.1D is the original standard for STP, and many improvements have enhanced the basic loop-free STP. You can create a separate loop-free path for each VLAN, which is named Per VLAN Spanning Tree (PVST+). Additionally, the entire standard was reworked to make the loop-free convergence process faster to keep up with the faster equipment. This STP standard with faster convergence is the 802.1w standard, which is known as Rapid Spanning Tree (RSTP).
Finally, the 802.1s standard, Multiple Spanning Trees (MST), allows you to map multiple VLANs into a single spanning tree instance. Each instance runs an independent spanning tree topology.
Although the software can interoperate with legacy 802.1D systems, the system runs Rapid PVST+ and MST. You can use either Rapid PVST+ or MST in a given VDC; you cannot mix both in one VDC. Rapid PVST+ is the default STP protocol for Cisco NX-OS for the Cisco Nexus 3000 Series.
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
4 |
OL-26590-01 |
Overview
Note Cisco NX-OS for the Cisco Nexus 3000 Series uses the extended system ID and MAC address reduction; you cannot disable these features.
In addition, Cisco has created some proprietary features to enhance the spanning tree activities.
Rapid PVST+
Rapid PVST+ is the default spanning tree mode for the software and is enabled by default on the default VLAN and all newly created VLANs.
A single instance, or topology, of RSTP runs on each configured VLAN, and each Rapid PVST+ instance on a VLAN has a single root device. You can enable and disable STP on a per-VLAN basis when you are running Rapid PVST+.
MST
The software also supports MST. The multiple independent spanning tree topologies enabled by MST provide multiple forwarding paths for data traffic, enable load balancing, and reduce the number of STP instances required to support a large number of VLANs.
MST incorporates RSTP, so it also allows rapid convergence. MST improves the fault tolerance of the network because a failure in one instance (forwarding path) does not affect other instances (forwarding paths).
Note Changing the spanning tree mode disrupts the traffic because all spanning tree instances are stopped for the previous mode and started for the new mode.
You can force specified interfaces to send prestandard, rather than standard, MST messages using the command-line interface.
The software supports the following Cisco proprietary features:
•Spanning tree port types—The default spanning tree port type is normal. You can configure interfaces connected to Layer 2 hosts as edge ports and interfaces connected to Layer 2 switches or bridges as network ports.
•Bridge Assurance—Once you configure a port as a network port, Bridge Assurance sends BPDUs on all ports and moves a port into the blocking state if it no longer receives BPDUs. This enhancement is available only when you are running Rapid PVST+ or MST.
•BPDU Guard—BPDU Guard shuts down the port if that port receives a BPDU.
•BPDU Filter—BPDU Filter suppresses sending and receiving BPDUs on the port.
•Loop Guard—Loop Guard prevents the nondesignated ports from transitioning to the STP forwarding state, which prevents loops in the network.
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
5 |
Overview
STP Extensions
• Root Guard—Root Guard prevents the port from becoming the root in an STP topology.
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
6 |
OL-26590-01 |
C H A P T E R 3
This chapter contains the following sections:
• |
Information About Ethernet Interfaces, |
page |
7 |
|
• |
Configuring Ethernet Interfaces, |
page |
11 |
|
• |
Displaying Interface Information, |
page |
21 |
|
• |
Displaying Input Packet Discard Information, |
page 23 |
||
• |
Default Physical Ethernet Settings , page 24 |
|
The Ethernet ports can operate as standard Ethernet interfaces connected to servers or to a LAN.
On a Cisco Nexus 3000 Series switch, the Ethernet interfaces are enabled by default.
You can enable the various capabilities of the Ethernet interfaces on a per-interface basis using the interface command. When you enter the interface command, you specify the following information:
• Interface type—All physical Ethernet interfaces use the ethernet keyword.
• Slot number
◦Slot 1 includes all the fixed ports.
◦Slot 2 includes the ports on the upper expansion module (if populated).
◦Slot 3 includes the ports on the lower expansion module (if populated).
• Port number
◦Port number within the group.
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
7 |
Configuring Ethernet Interfaces
The interface numbering convention is extended to support use with a Cisco Nexus 2000 Series Fabric Extender as follows:
switch(config)# interface ethernet [chassis/]slot/port
•Chassis ID is an optional entry to address the ports of a connected Fabric Extender. The chassis ID is configured on a physical Ethernet or EtherChannel interface on the switch to identify the Fabric Extender discovered via the interface. The chassis ID ranges from 100 to 199.
About the Unidirectional Link Detection Parameter
The Cisco-proprietary Unidirectional Link Detection (UDLD) protocol allows ports that are connected through fiber optics or copper (for example, Category 5 cabling) Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. When the switch detects a unidirectional link, UDLD shuts down the affected LAN port and alerts the user. Unidirectional links can cause a variety of problems, including spanning tree topology loops.
UDLD is a Layer 2 protocol that works with the Layer 1 protocols to determine the physical status of a link. At Layer 1, autonegotiation takes care of physical signaling and fault detection. UDLD performs tasks that autonegotiation cannot perform, such as detecting the identities of neighbors and shutting down misconnected LAN ports. When you enable both autonegotiation and UDLD, Layer 1 and Layer 2 detections work together to prevent physical and logical unidirectional connections and the malfunctioning of other protocols.
A unidirectional link occurs whenever traffic transmitted by the local device over a link is received by the neighbor but traffic transmitted from the neighbor is not received by the local device. If one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up. In this case, the logical link is undetermined, and UDLD does not take any action. If both fibers are working normally at Layer 1, then UDLD at Layer 2 determines whether those fibers are connected correctly and whether traffic is flowing bidirectionally between the correct neighbors. This check cannot be performed by autonegotiation, because autonegotiation operates at Layer 1.
A Cisco Nexus 3000 Series switch periodically transmits UDLD frames to neighbor devices on LAN ports with UDLD enabled. If the frames are echoed back within a specific time frame and they lack a specific acknowledgment (echo), the link is flagged as unidirectional and the LAN port is shut down. Devices on both ends of the link must support UDLD in order for the protocol to successfully identify and disable unidirectional links.
Note By default, UDLD is locally disabled on copper LAN ports to avoid sending unnecessary control traffic on this type of media.
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
8 |
OL-26590-01 |
Configuring Ethernet Interfaces
About the Unidirectional Link Detection Parameter
The following figure shows an example of a unidirectional link condition. Device B successfully receives traffic from Device A on the port. However, Device A does not receive traffic from Device B on the same port. UDLD detects the problem and disables the port.
Figure 1: Unidirectional Link
The following table shows the default UDLD configuration.
Table 2: UDLD Default Configuration |
|
Feature |
Default Value |
UDLD global enable state
UDLD aggressive mode
UDLD per-port enable state for fiber-optic media
UDLD per-port enable state for twisted-pair (copper) media
Globally disabled
Disabled
Enabled on all Ethernet fiber-optic LAN ports
Disabled on all Ethernet 10/100 and 1000BASE-TX LAN ports
UDLD aggressive mode is disabled by default. You can configure UDLD aggressive mode only on point-to-point links between network devices that support UDLD aggressive mode. If UDLD aggressive mode is enabled, when a port on a bidirectional link that has a UDLD neighbor relationship established stops receiving UDLD frames, UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.
To prevent spanning tree loops, nonaggressive UDLD with the default interval of 15 seconds is fast enough to shut down a unidirectional link before a blocking port transitions to the forwarding state (with default spanning tree parameters).
When you enable the UDLD aggressive mode, the following occurs:
•One side of a link has a port stuck (both transmission and receive)
•One side of a link remains up while the other side of the link is down
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
9 |
Configuring Ethernet Interfaces
In these cases, the UDLD aggressive mode disables one of the ports on the link, which prevents traffic from being discarded.
About Interface Speed
A Cisco Nexus 3000 Series switch has a number of fixed 10-Gigabit ports, each equipped with SFP+ interface adapters.
The Cisco Discovery Protocol (CDP) is a device discovery protocol that runs over Layer 2 (the data link layer) on all Cisco-manufactured devices (routers, bridges, access servers, and switches) and allows network management applications to discover Cisco devices that are neighbors of already known devices. With CDP, network management applications can learn the device type and the Simple Network Management Protocol (SNMP) agent address of neighboring devices running lower-layer, transparent protocols. This feature enables applications to send SNMP queries to neighboring devices.
CDP runs on all media that support Subnetwork Access Protocol (SNAP). Because CDP runs over the data-link layer only, two systems that support different network-layer protocols can learn about each other.
Each CDP-configured device sends periodic messages to a multicast address, advertising at least one address at which it can receive SNMP messages. The advertisements also contain time-to-live, or holdtime information, which is the length of time a receiving device holds CDP information before discarding it. Each device also listens to the messages sent by other devices to learn about neighboring devices.
The switch supports both CDP Version 1 and Version 2.
The following table shows the default CDP configuration.
Table 3: Default CDP Configuration |
|
Feature |
Default Setting |
CDP interface state |
Enabled |
CDP timer (packet update frequency) |
60 seconds |
CDP holdtime (before discarding) |
180 seconds |
CDP Version-2 advertisements |
Enabled |
An interface is in the error-disabled (err-disabled) state when the inteface is enabled administratively (using the no shutdown command) but disabled at runtime by any process. For example, if UDLD detects a unidirectional link, the interface is shut down at runtime. However, because the interface is administratively
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
10 |
OL-26590-01 |
enabled, the interface status displays as err-disabled. Once an interface goes into the err-disabled state, you must manually reenable it or you can configure an automatic timeout recovery value. The err-disabled detection is enabled by default for all causes. The automatic recovery is not configured by default.
When an interface is in the err-disabled state, use the errdisable detect cause command to find information about the error.
You can configure the automatic err-disabled recovery timeout for a particular err-disabled cause by changing the time variable.
The errdisable recovery cause command provides automatic recovery after 300 seconds. To change the recovery period, use the errdisablerecoveryinterval command to specify the timeout period. You can specify 30 to 65535 seconds.
If you do not enable the err-disabled recovery for the cause, the interface stays in the err-disabled state until you enter the shutdown and no shutdown commands. If the recovery is enabled for a cause, the interface is brought out of the err-disabled state and allowed to retry operation once all the causes have timed out. Use the show interface status err-disabled command to display the reason behind the error.
About Port Profiles
The Cisco Nexus 3000 Series device does not support Port Profiles.
The Cisco Nexus 3000 Series device does not support Port Profiles.
The debounce timer feature is not supported on Nexus 3000.
The Cisco Nexus 3000 Series switch does not fragment frames. As a result, the switch cannot have two ports in the same Layer 2 domain with different maximum transmission units (MTUs). A per-physical Ethernet interface MTU is not supported. Instead, the MTU is set according to the QoS classes. You modify the MTU by setting Class and Policy maps.
Note When you show the interface settings, a default MTU of 1500 is displayed for physical Ethernet interfaces.
Configuring Ethernet Interfaces
The section includes the following topics:
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
11 |
Configuring Ethernet Interfaces
Configuring the UDLD Mode
You can configure normal or aggressive unidirectional link detection (UDLD) modes for Ethernet interfaces on devices configured to run UDLD. Before you can enable a UDLD mode for an interface, you must make sure that UDLD is already enabled on the device that includes the interface. UDLD must also be enabled on the other linked interface and its device.
To use the normal UDLD mode, you must configure one of the ports for normal mode and configure the other port for the normal or aggressive mode. To use the aggressive UDLD mode, you must configure both ports for the aggressive mode.
Note Before you begin, UDLD must be enabled for the other linked port and its device.
To configure the UDLD mode, perform this task:
Procedure
|
Command or Action |
Purpose |
Step 1 |
switch# configure terminal |
Enters configuration mode. |
Step 2 |
switch(config)# feature udld |
Enables UDLD for the device. |
Step 3 |
switch(config)# no feature udld |
Disables UDLD for the device. |
Step 4 |
switch(config)# show udld global |
Displays the UDLD status for the device. |
Step 5 |
switch(config)# interface type slot/port |
Specifies an interface to configure, and enters |
|
|
interface configuration mode. |
Step 6 |
switch(config-if)# udld {enable | disable |
Enables the normal UDLD mode, disables |
|
| aggressive} |
UDLD, or enables the aggressive UDLD mode. |
Step 7 |
switch(config-if)# show udld interface |
Displays the UDLD status for the interface. |
This example shows how to enable the UDLD for the switch:
switch# configure terminal switch(config)# feature udld
This example shows how to enable the normal UDLD mode for an Ethernet port:
switch# configure terminal switch(config)# interface ethernet 1/4 switch(config-if)# udld enable
This example shows how to enable the aggressive UDLD mode for an Ethernet port:
switch# configure terminal switch(config)# interface ethernet 1/4 switch(config-if)# udld aggressive
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
12 |
OL-26590-01 |
Configuring Ethernet Interfaces
This example shows how to disable UDLD for an Ethernet port:
switch# configure terminal switch(config)# interface ethernet 1/4 switch(config-if)# udld disable
This example shows how to disable UDLD for the switch:
switch# configure terminal switch(config)# no feature udld
Changing an Interface Port Mode
You can configure a Quad small form-factor pluggable (QSFP+) port by using the hardwareprofileportmode command. To restore the defaults, use the no form of this command.
To change an interface port mode, preform this task:
Procedure
|
Command or Action |
Purpose |
|
Step 1 |
switch# configure terminal |
Enters global configuration mode. |
|
Step 2 |
switch(config)# copy |
Copies the running configuration to the bootflash. You |
|
|
running-config bootflash: |
can use this file to configure your device later. |
|
|
my-config.cfg |
|
|
Step 3 |
switch(config)# write erase |
Removes all the interface configurations. |
|
Step 4 |
switch(config)# reload |
Reloads the Cisco Nexus 3000 Series switch software. |
|
Step 5 |
switch(config)# [no] hardware |
Changes the interface port mode. |
|
|
profile portmode portmode |
|
|
Step 6 |
switch(config)# copy |
(Optional) |
|
|
running-config startup-config |
Saves the change persistently through reboots and restarts |
|
|
|
by copying the running configuration to the startup |
|
|
|
configuration. |
|
Step 7 |
switch(config)# reload |
Reloads the Cisco Nexus 3000 Series switch software. |
|
|
|
Manually apply all the interface configuration. You can |
|
|
|
refer to the configuration file that you saved earlier. |
|
|
|
Note |
The interface numbering changes if the ports |
|
|
|
are changed from 40G mode to 4x10G mode or |
|
|
|
vice-versa. |
This example shows how to change the port mode to 48x10g+4x40g for QSFP+ ports:
switch# configure terminal
switch(config) copy running-config bootflash:my-config.cfg switch(config)# write erase
switch(config)# reload
WARNING: This command will reboot the system Do you want to continue? (y/n) [n] y
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
13 |
Configuring Ethernet Interfaces
switch(config)# hardware profile portmode 48x10g+4x40g
Warning: This command will take effect only after saving the configuration and reload! Port configurations could get lost when port mode is changed!
switch(config)# copy running-config startup-config switch(config)# reload
WARNING: This command will reboot the system Do you want to continue? (y/n) [n] y
This example shows how to change the port mode to 48x10g+4x40g for QSFP+ ports and verify the changes:
switch# configure terminal
switch(config)# hardware profile portmode 48x10g+4x40g
Warning: This command will take effect only after saving the configuration and r eload! Port configurations could get lost when port mode is changed! switch(config)# show running-config
!Command: show running-config !Time: Thu Aug 25 07:39:37 2011 version 5.0(3)U2(1)
feature telnet no feature ssh feature lldp
username admin password 5 $1$OOV4MdOM$BAB5RkD22YanT4empqqSM0 role network-admin ip domain-lookup
switchname BLR-QG-5 ip access-list my-acl
10 deny ip any 10.0.0.1/32
20 deny ip 10.1.1.1/32 any
class-map type control-plane match-any copp-arp class-map type control-plane match-any copp-bpdu
:
:
control-plane
service-policy input copp-system-policy hardware profile tcam region arpacl 128 hardware profile tcam region ifacl 256 hardware profile tcam region racl 256 hardware profile tcam region vacl 512 hardware profile portmode 48x10G+4x40G
snmp-server user admin network-admin auth md5 0xdd1d21ee42e93106836cdefd1a60e062 <--Output truncated-->
switch#
This example shows how to restore the default port mode for QSFP+ ports:
switch# configure terminal
switch(config)# no hardware profile portmode
Warning: This command will take effect only after saving the configuration and r eload! Port configurations could get lost when port mode is changed! switch(config)#
Configuring Interface Speed
Procedure
|
Command or Action |
Purpose |
Step 1 |
switch# configure terminal |
Enters configuration mode. |
Step 2 |
switch(config)# interface type |
Enters interface configuration mode for the specified |
|
slot/port |
interface. This interface must have a 1-Gigabit Ethernet SFP |
|
|
transceiver inserted into it. |
Step 3 |
switch(config-if)# speed speed |
Sets the speed on the interface. |
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
14 |
OL-26590-01 |
Configuring Ethernet Interfaces
Command or Action |
Purpose |
This command can only be applied to a physical Ethernet interface. The speed argument can be set to one of the following:
• 10 Mbps
• 100 Mbps
• 1 Gbps
• 10Gbps
• automatic
The following example shows how to set the speed for a 1-Gigabit Ethernet port:
switch# configure terminal switch(config)# interface ethernet 1/4 switch(config-if)# speed 1000
Note If the interface and transceiver speed is mismatched, the SFP validation failed message is displayed when you enter the show interface ethernet slot/port command. For example, if you insert a 1-Gigabit SFP transceiver into a port without configuring the speed 1000 command, you will get this error. By default, all ports are 10 Gigabits.
Disabling Link Negotiation
You can disable link negotiation using the nonegotiateauto command. By default, auto-negotiation is enabled on 1-Gigabit ports and disabled on 10-Gigabit ports. By default, auto-negotiation is enabled on the Cisco Nexus 3064 and 3064-X switches and disabled on the Cisco Nexus 3048 switch.
This command is equivalent to the IOS speed non-negotiate command.
Note Cisco does not recommend that you to enable auto negotiation on 10-Gigabit ports. Enabling auto-negotiation on 10-Gigabit ports brings the link down. By default, link negotiation is disabled on 10-Gigabit ports.
Procedure
|
Command or Action |
Purpose |
Step 1 |
switch# configure terminal |
Enters configuration mode. |
Step 2 |
switch(config)# interface ethernet |
Selects the interface and enters interface mode. |
|
slot/port |
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 |
15 |
Configuring Ethernet Interfaces
|
Command or Action |
Purpose |
Step 3 |
switch(config-if)# no negotiate auto |
Disables link negotiation on the selected Ethernet |
|
|
interface (1-Gigabit port). |
Step 4 |
switch(config-if)# negotiate auto |
(Optional) |
|
|
Enables link negotiation on the selected Ethernet |
|
|
interface. The default for 1-Gigabit ports is enabled. |
This example shows how to disable auto negotiation on a specified Ethernet interface (1-Gigabit port): switch# configure terminal
switch(config)# interface ethernet 1/1 switch(config-if)# no negotiate auto switch(config-if)#
This example shows how to enable auto negotiation on a specified Ethernet interface (1-Gigabit port): switch# configure terminal
switch(config)# interface ethernet 1/5 switch(config-if)# negotiate auto switch(config-if)#
Configuring the CDP Characteristics
You can configure the frequency of Cisco Discovery Protocol (CDP) updates, the amount of time to hold the information before discarding it, and whether or not to send Version-2 advertisements.
To configure CDP characteristics for an interface, perform this task:
Procedure
|
Command or Action |
Purpose |
Step 1 |
switch# configure terminal |
Enters configuration mode. |
Step 2 |
switch(config)# [no] cdp |
(Optional) |
|
advertise {v1 | v2 } |
Configures the version to use to send CDP advertisements. |
|
|
Version-2 is the default state. |
|
|
Use the no form of the command to return to its default |
|
|
setting. |
Step 3 |
switch(config)# [no] cdp format |
(Optional) |
|
device-id {mac-address | |
Configures the format of the CDP device ID. The default is |
|
serial-number | system-name} |
the system name, which can be expressed as a fully qualified |
|
|
domain name. |
|
|
Use the no form of the command to return to its default |
|
|
setting. |
Step 4 |
switch(config)# [no] cdp |
(Optional) |
|
holdtime seconds |
Specifies the amount of time a receiving device should hold |
|
|
the information sent by your device before discarding it. The |
|
|
range is 10 to 255 seconds; the default is 180 seconds. |
|
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1) |
16 |
OL-26590-01 |