Cisco Systems N3KC3048TP1GE, N3KC3064TFAL3 User Manual
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
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.
CONTENTS
Preface
CHAPTER 1
CHAPTER 2
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
CHAPTER 3
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
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
CHAPTER 4
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
CHAPTER 5
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
CHAPTER 6
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
CHAPTER 7
CHAPTER 8
Configuring Switching Modes 59
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
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
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
CHAPTER 9
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
Verifying MST Configurations 112
CHAPTER 10
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
CHAPTER 11
CHAPTER 12
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
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
CHAPTER 13
CHAPTER 14
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
Preface
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
•
Audience
This publication is for experienced network administrators who configure and maintain Cisco Nexus Series
devices.
Document Conventions
Command descriptions use the following conventions:
DescriptionConvention
bold
Italic
[x | y]
{x | y}
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 xi
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]
Square brackets enclosing keywords or arguments separated by a vertical
bar indicate an optional choice.
Braces enclosing keywords or arguments separated by a vertical bar
indicate a required choice.
Related Documentation for Nexus 3000 Series NX-OS Software
Preface
DescriptionConvention
[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:
DescriptionConvention
Terminal sessions and information the switch displays are in screen font.screen font
Information you must enter is in boldface screen font.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
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
CHAPTER 1
New and Changed Information for this Release
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
•
New and Changed Information for this Release
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
Switching Modes
DescriptionFeature
switching mode. There are two switching
modes: cut-through and store-and-forward.
Changed
in
Release
5.0(3)U3(1)Added a new chapter about configuring your
Where DocumentedAdded or
Configuring Switching
Modes, on page 59
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
Overview
This chapter contains the following sections:
Layer 2 Ethernet Switching Overview, page 3
•
VLANs, page 3
•
Private VLANs, page 4
•
Spanning Tree , page 4
•
Layer 2 Ethernet Switching Overview
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.
CHAPTER 2
VLANs
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
Private VLANs
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.
Inter-Switch Link (ISL) trunking is not supported on the NX-OS software for the Cisco Nexus 3000 Series.Note
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.
Overview
Spanning Tree
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 Overview
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
Rapid PVST+
Note
Rapid PVST+
MST
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+ 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+.
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.
STP Extensions
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
STP Extensions
Overview
• 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
CHAPTER 3
Configuring Ethernet Interfaces
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
•
Information About Ethernet Interfaces
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.
About the Interface Command
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
About the Unidirectional Link Detection Parameter
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.
Configuring Ethernet Interfaces
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
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
Default UDLD Configuration
About the Unidirectional Link Detection Parameter
The following table shows the default UDLD configuration.
Table 2: UDLD Default Configuration
UDLD per-port enable state for twisted-pair (copper)
media
UDLD Aggressive and Nonaggressive Modes
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:
Default ValueFeature
Globally disabledUDLD global enable state
DisabledUDLD aggressive mode
Enabled on all Ethernet fiber-optic LAN portsUDLD per-port enable state for fiber-optic media
Disabled on all Ethernet 10/100 and 1000BASE-TX
LAN ports
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
About Interface Speed
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.
About the Cisco Discovery Protocol
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.
Configuring Ethernet Interfaces
Default CDP Configuration
The following table shows the default CDP configuration.
Table 3: Default CDP Configuration
About the Error-Disabled State
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
Default SettingFeature
EnabledCDP interface state
60 secondsCDP timer (packet update frequency)
180 secondsCDP holdtime (before discarding)
EnabledCDP Version-2 advertisements
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
10 OL-26590-01
Configuring Ethernet Interfaces
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 errdisable recovery interval 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
About Port Profiles
The Cisco Nexus 3000 Series device does not support Port Profiles.
Guidelines and Limitations for Port Profiles
The Cisco Nexus 3000 Series device does not support Port Profiles.
About the Debounce Timer Parameters
The debounce timer feature is not supported on Nexus 3000.
About MTU Configuration
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.
When you show the interface settings, a default MTU of 1500 is displayed for physical Ethernet interfaces.Note
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 the UDLD Mode
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.
Before you begin, UDLD must be enabled for the other linked port and its device.Note
To configure the UDLD mode, perform this task:
Procedure
Configuring Ethernet Interfaces
PurposeCommand or Action
Step 1
Step 2
Step 3
Step 4
Step 5
switch(config)# interface type slot/port
Enters configuration mode.switch# configure terminal
Enables UDLD for the device.switch(config)# feature udld
Disables UDLD for the device.switch(config)# no feature udld
Displays the UDLD status for the device.switch(config)# show udld global
Specifies an interface to configure, and enters
interface configuration mode.
Step 6
Step 7
switch(config-if)# udld {enable | disable
| aggressive}
switch(config-if)# show udld interface
Enables the normal UDLD mode, disables
UDLD, or enables the aggressive UDLD mode.
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 hardware profile portmode
command. To restore the defaults, use the no form of this command.
To change an interface port mode, preform this task:
Procedure
Changing an Interface Port Mode
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
switch(config)# copy
running-config bootflash:
my-config.cfg
profile portmode portmode
switch(config)# copy
running-config startup-config
PurposeCommand or Action
Enters global configuration mode.switch# configure terminal
Copies the running configuration to the bootflash. You
can use this file to configure your device later.
Removes all the interface configurations.switch(config)# write erase
Reloads the Cisco Nexus 3000 Series switch software.switch(config)# reload
Changes the interface port mode.switch(config)# [no] hardware
(Optional)
Saves the change persistently through reboots and restarts
by copying the running configuration to the startup
configuration.
Reloads the Cisco Nexus 3000 Series switch software.switch(config)# reload
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 Interface Speed
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 Ethernet Interfaces
Configuring Interface Speed
Procedure
PurposeCommand or Action
Step 1
Step 2
switch(config)# interface type
slot/port
Step 3
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
14 OL-26590-01
switch(config-if)# speed speed
Enters configuration mode.switch# configure terminal
Enters interface configuration mode for the specified
interface. This interface must have a 1-Gigabit Ethernet SFP
transceiver inserted into it.
Sets the speed on the interface.
Configuring Ethernet Interfaces
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
Disabling Link Negotiation
PurposeCommand or Action
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
•
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 no negotiate auto 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
PurposeCommand or Action
Step 1
Step 2
Enters configuration mode.switch# configure terminal
Selects the interface and enters interface mode.switch(config)# interface ethernet
slot/port
Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
OL-26590-01 15
Configuring the CDP Characteristics
Configuring Ethernet Interfaces
PurposeCommand or Action
Step 3
Step 4
switch(config-if)# no negotiate auto
switch(config-if)# negotiate auto
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:
Disables link negotiation on the selected Ethernet
interface (1-Gigabit port).
(Optional)
Enables link negotiation on the selected Ethernet
interface. The default for 1-Gigabit ports is enabled.
Procedure
Step 1
Step 2
Step 3
Step 4
switch(config)# [no] cdp
advertise {v1 | v2 }
switch(config)# [no] cdp format
device-id {mac-address |
serial-number | system-name}
switch(config)# [no] cdp
holdtime seconds
PurposeCommand or Action
Enters configuration mode.switch# configure terminal
(Optional)
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.
(Optional)
Configures the format of the CDP device ID. The default is
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.
(Optional)
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
Loading...