H3C S5120-EI Series User manual

H3C S5120-EI Switch Series
Layer 2 - LAN Switching Configuration Guide
Hangzhou H3C Technologies Co., Ltd.
http://www.h3c.com
Software version: Release 2210
Document version: 6W100-20110915

Copyright © 2011, Hangzhou H3C Technologies Co., Ltd. and its licensors
All rights reserved
No part of this manual may be reproduced or transmitted in any form or by any means without prior
written consent of Hangzhou H3C Technologies Co., Ltd.
Trademarks
H3C, , Aolynk, , H3Care,
, TOP G, , IRF, NetPilot, Neocean, NeoVTL,
SecPro, SecPoint, SecEngine, SecPath, Comware, Secware, Storware, NQA, VVG, V2G, VnG, PSPT,
XGbus, N-Bus, TiGem, InnoVision and HUASAN are trademarks of Hangzhou H3C Technologies Co.,
Ltd.
All other trademarks that may be mentioned in this manual are the property of their respective owners
Notice
The information in this document is subject to change without notice. Every effort has been made in the
preparation of this document to ensure accuracy of the contents, but all statements, information, and
recommendations in this document do not constitute the warranty of any kind, express or implied.

Preface
The H3C S5120-EI documentation set includes 10 configuration guides, which describe the software
features for the H3C S5120-EI Switch Series Release 2210, and guide you through the software
configuration procedures. These configuration guides also provide configuration examples to help you
apply software features to different network scenarios.
The Layer 2—LAN Switching Configuration Guide describes LAN switching fundamentals and
configuration. It describes how to implement flow control and load sharing, isolate uses in the same
VLAN, eliminate Layer 2 loops, and divide VLANs.
This preface includes:
•Audience
•New and changed features
•Conventions
•About the S5120-EI documentation set
•Obtaining documentation
•Technical support
•Documentation feedback
Audience
This documentation is intended for:
•Network planners
•Field technical support and servicing engineers
•Network administrators working with the S5120-EI Switch Series
New and changed features
This section describes the new and changed features in software release 2210 over release 2208 for the
S5120-EI switches.
Feature module New features Changed features
Ethernet interface Restoring the default settings of an
Ethernet port N/A
Loopback interface
and null interfaces
Restoring the default settings of a
loopback or null interface N/A
MAC address
management
MAC address table: MAC address
roaming N/A

Feature module New features Changed features
Ethernet link
aggregation
•Restoring the default setting of an
aggregate interface
•Limiting the number of selected ports in
an aggregation group
•Assigning aggregation priority to
ports in a static aggregation group
N/A
Port isolation N/A N/A
Spanning tree •PVST
•TC snooping N/A
BPDU tunneling N/A N/A
VLAN
Common VLAN:
•Restoring the default settings of a
VLAN interface
•Setting the MTU of a VLAN interface
Isolate-user-VLAN:
•Adding trunk ports to
isolate-user-VLANs or secondary
VLANs
•After you associate a secondary VLAN
with an isolate-user-VLAN, you can still
perform the following tasks:
{Adding/removing access ports
to/from the isolate-user-VLAN and
secondary VLAN
{Deleting the isolate-user-VLAN or the
secondary VLAN
{Using the isolated-vlan enable
command to enable Layer 2
isolation between the ports in the
secondary VLAN
{Changing the promiscuous or host
mode of the ports in the VLANs
GVRP N/A N/A
QinQ N/A N/A
LLDP N/A N/A
Conventions
This section describes the conventions used in this documentation set.
Command conventions
Convention Description
Boldface Bold text represents commands and keywords that you enter literally as shown.
Italic Italic text represents arguments that you replace with actual values.
[ ] Square brackets enclose syntax choices (keywords or arguments) that are optional.
{ x | y | ... }
Braces enclose a set of required syntax choices separated by vertical bars, from which
you select one.

Convention Description
[ x | y | ... ]
Square brackets enclose a set of optional syntax choices separated by vertical bars, from
which you select one or none.
{ x | y | ... } *
Asterisk marked braces enclose a set of required syntax choices separated by vertical
bars, from which you select at least one.
[ x | y | ... ] *
Asterisk marked square brackets enclose optional syntax choices separated by vertical
bars, from which you select one choice, multiple choices, or none.
&<1-n> The argument or keyword and argument combination before the ampersand (&) sign can
be entered 1 to n times.
# A line that starts with a pound (#) sign is comments.
GUI conventions
Convention Description
Boldface Window names, button names, field names, and menu items are in Boldface. For
example, the New User window appears; click OK.
> Multi-level menus are separated by angle brackets. For example, File > Create > Folder.
Symbols
Convention Description
WARNING An alert that calls attention to important information that if not understood or followed can
result in personal injury.
CAUTION An alert that calls attention to important information that if not understood or followed can
result in data loss, data corruption, or damage to hardware or software.
IMPORTANT An alert that calls attention to essential information.
NOTE An alert that contains additional or supplementary information.
TIP An alert that provides helpful information.
Network topology icons
Represents a generic network device, such as a router, switch, or firewall.
Represents a routing-capable device, such as a router or Layer 3 switch.
Represents a generic switch, such as a Layer 2 or Layer 3 switch, or a router that supports
Layer 2 forwarding and other Layer 2 features.
Port numbering in examples
The port numbers in this document are for illustration only and might be unavailable on your device.

About the S5120-EI documentation set
The H3C S5120-EI documentation set includes:
Documents Purposes
Product description and specifications
Marketing brochure Describe product specifications and benefits.
Technology white papers Provide an in-depth description of software features and
technologies.
Hardware specifications and installation
Compliance and safety manual
CE DOCs
Provide regulatory information and the safety instructions that must be
followed during installation.
Installation quick start Guides you through initial installation and setup procedures to help
you quickly set up your device.
Installation manual Provides a complete guide to switch installation and specifications.
RPS Ordering Information for H3C
Low-End Ethernet Switches Helps you order RPSs for switches that can work with an RPS.
User manuals for RPSs Describe the specifications, installation, and replacement of RPSs.
User manuals for interface cards Describe the specifications, installation, and replacement of
expansion interface cards.
H3C Low End Series Ethernet Switches
Pluggable Modules Manual Describes the specifications of pluggable transceiver modules.
Pluggable SFP[SFP+][XFP] Transceiver
Modules Installation Guide
Describe the installation, and replacement of SFP/SFP+/XFP
transceiver modules.
Software configuration
Configuration guides Describe software features and configuration procedures.
Command references Provide a quick reference to all available commands.
Operations and maintenance
H3C Series Ethernet Switches Login
Password Recovery Manual Helps you deal with switch login password loss.
Release notes
Provide information about the product release, including the version
history, hardware and software compatibility matrix, version
upgrade information, technical support information, and software
upgrading.
Obtaining documentation
You can access the most up-to-date H3C product documentation on the World Wide Web at
http://www.h3c.com.
Click the links on the top navigation bar to obtain different categories of product documentation:
[Technical Support & Documents > Technical Documents] – Provides hardware installation, software
upgrading, and software feature configuration and maintenance documentation.
[Products & Solutions] – Provides information about products and technologies, as well as solutions.

[Technical Support & Documents > Software Download] – Provides the documentation released with the
software version.
Technical support
cu[email protected]
http://www.h3c.com
Documentation feedback
You can e-mail your comments about product documentation to inf[email protected].
We appreciate your comments.

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Contents
Ethernet interface configuration ·································································································································· 1
Ethernet interface naming conventions ···························································································································1
Configuring a combo interface ·······································································································································1
Introduction to combo interfaces·····························································································································1
Configuration prerequisites ·····································································································································1
Changing the active port of a combo interface····································································································1
Configuring basic settings of an Ethernet interface·······································································································2
Shutting down an Ethernet interface ·······························································································································3
Setting speed options for auto negotiation on an Ethernet interface···········································································3
Configuring flow control on an Ethernet interface·········································································································4
Configuring link change suppression on an Ethernet interface····················································································5
Configuring link-down event suppression ··············································································································5
Configuring link-up event suppression ···················································································································6
Configuring loopback testing on an Ethernet interface·································································································6
Configuring jumbo frame support ···································································································································7
Configuring a port group·················································································································································7
Enabling energy saving functions on an Ethernet interface··························································································8
Enabling auto power-down ·····································································································································8
Configuring storm suppression ········································································································································9
Setting the statistics polling interval·································································································································9
Enabling loopback detection on an Ethernet interface ······························································································ 10
Setting the MDI mode of an Ethernet interface ··········································································································· 12
Enabling bridging on an Ethernet interface ················································································································ 13
Testing the cable connection of an Ethernet interface································································································ 13
Configuring storm control on an Ethernet interface···································································································· 14
Displaying and maintaining an Ethernet interface ····································································································· 15
Loopback and null interface configuration···············································································································17
Configuring a loopback interface ································································································································ 17
Introduction to the loopback interface················································································································· 17
Configuration procedure ······································································································································ 17
Configuring the null interface ······································································································································· 18
Introduction to the null interface··························································································································· 18
Configuration procedure ······································································································································ 18
Displaying and maintaining loopback and null interfaces························································································ 18
MAC address table configuration·····························································································································20
Overview········································································································································································· 20
How a MAC address table entry is created······································································································· 20
Types of MAC address table entries ··················································································································· 20
MAC address table-based frame forwarding ···································································································· 21
Configuring the MAC address table···························································································································· 21
Configuring static, dynamic, and blackhole MAC address table entries ······················································· 21
Disabling MAC address learning························································································································ 22
Configuring the aging timer for dynamic MAC address entries ······································································ 23
Configuring the MAC learning limit on ports····································································································· 23
Enabling MAC address roaming························································································································· 24
Displaying and maintaining MAC address tables ····································································································· 26
MAC address table configuration example ················································································································ 26

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MAC Information configuration ································································································································28
Overview········································································································································································· 28
Introduction to MAC Information ························································································································· 28
How MAC Information works ······························································································································ 28
Configuring MAC Information······································································································································ 28
Enabling MAC Information globally ··················································································································· 28
Enabling MAC Information on an interface ······································································································· 28
Configuring MAC Information mode ·················································································································· 29
Configuring the interval for sending Syslog or trap messages········································································· 29
Configuring the MAC Information queue length································································································ 29
MAC Information configuration example···················································································································· 30
Ethernet link aggregation configuration···················································································································31
Overview········································································································································································· 31
Basic concepts ······················································································································································· 31
Aggregating links in static mode ························································································································· 34
Aggregating links in dynamic mode ··················································································································· 35
Load-sharing criteria for link aggregation groups ····························································································· 37
Ethernet link aggregation configuration task list········································································································· 37
Configuring an aggregation group ····························································································································· 38
Configuration guidelines ······································································································································ 38
Configuring a static aggregation group············································································································· 38
Configuring a dynamic aggregation group ······································································································· 39
Configuring an aggregate interface ···························································································································· 40
Configuring the description of an aggregate interface····················································································· 40
Enabling link state traps for an aggregate interface ························································································· 40
Setting the minimum number of Selected ports for an aggregation group ····················································· 41
Shutting down an aggregate interface ··············································································································· 41
Restoring the default settings for an aggregate interface ················································································· 42
Configuring load sharing for link aggregation groups······························································································ 42
Configuring load-sharing criteria for link aggregation groups ········································································ 42
Enabling local-first load sharing for link aggregation······················································································· 43
Enabling link-aggregation traffic redirection··············································································································· 44
Displaying and maintaining Ethernet link aggregation ····························································································· 45
Ethernet link aggregation configuration examples····································································································· 45
Static aggregation configuration example ········································································································· 46
Dynamic aggregation configuration example ··································································································· 48
Port isolation configuration········································································································································51
Introduction to port isolation ········································································································································· 51
Assigning a port to the isolation group ······················································································································· 51
Displaying and maintaining isolation groups ············································································································· 51
Port isolation configuration example···························································································································· 52
Spanning tree configuration······································································································································53
STP ··················································································································································································· 53
STP protocol packets ············································································································································· 53
Basic concepts in STP············································································································································ 54
Calculation process of the STP algorithm ··········································································································· 55
RSTP················································································································································································· 60
PVST················································································································································································· 61
MSTP················································································································································································ 61
STP, RSTP, and PVST limitations ·························································································································· 61
MSTP features ························································································································································ 61
MSTP basic concepts ············································································································································ 61
How MSTP works ·················································································································································· 65

iii
Implementation of MSTP on devices···················································································································· 66
Protocols and standards ················································································································································ 66
Spanning tree configuration task list···························································································································· 66
Configuring the spanning tree······································································································································ 71
Setting the spanning tree mode ··························································································································· 71
Configuring an MST region ································································································································· 71
Configuring the root bridge or a secondary root bridge·················································································· 72
Configuring the device priority···························································································································· 73
Configuring the maximum hops of an MST region ··························································································· 74
Configuring the network diameter of a switched network················································································ 74
Configuring spanning tree timers ························································································································ 75
Configuring the timeout factor ····························································································································· 76
Configuring the maximum port rate ···················································································································· 77
Configuring edge ports········································································································································· 77
Configuring path costs of ports···························································································································· 78
Configuring the port priority ································································································································ 80
Configuring the port link type ······························································································································ 81
Configuring the mode a port uses to recognize/send MSTP packets ····························································· 81
Enabling the output of port state transition information ···················································································· 82
Enabling the spanning tree feature ····················································································································· 82
Performing mCheck··············································································································································· 84
Configuring Digest Snooping······························································································································· 84
Configuring No Agreement Check······················································································································ 86
Configuring TC snooping ····································································································································· 88
Configuring protection functions·························································································································· 90
Displaying and maintaining the spanning tree··········································································································· 93
Spanning tree configuration examples························································································································ 93
MSTP configuration example ······························································································································· 93
PVST configuration example ································································································································ 97
BPDU tunneling configuration ································································································································ 101
Introduction to BPDU tunneling ···································································································································101
Background··························································································································································101
BPDU tunneling implementation·························································································································102
Configuring BPDU tunneling ·······································································································································103
Configuration prerequisites ································································································································103
Enabling BPDU tunneling····································································································································104
Configuring destination multicast MAC address for BPDUs ···········································································104
BPDU tunneling configuration examples····················································································································105
BPDU tunneling for STP configuration example ·······························································································105
BPDU tunneling for PVST configuration example·····························································································106
VLAN configuration ················································································································································ 108
Overview·······································································································································································108
VLAN ····································································································································································108
VLAN fundamentals·············································································································································108
VLAN types ··························································································································································109
Protocols and standards ·····································································································································110
Configuring basic VLAN settings································································································································110
Configuring basic settings of a VLAN interface ·······································································································111
VLAN interface overview····································································································································111
Configuration procedure ····································································································································111
VLAN interface configuration example·············································································································112
Port-based VLAN configuration ··································································································································113
Introduction to port-based VLAN ·······················································································································113

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Assigning an access port to a VLAN ················································································································114
Assigning a trunk port to a VLAN······················································································································115
Assigning a hybrid port to a VLAN···················································································································116
Port-based VLAN configuration example··········································································································117
MAC-based VLAN configuration································································································································119
Introduction to MAC-based VLAN ·····················································································································119
Configuring a MAC-based VLAN······················································································································121
MAC-based VLAN configuration example ·······································································································123
Protocol-based VLAN configuration ···························································································································126
Introduction to protocol-based VLAN ················································································································126
Configuring a protocol-based VLAN·················································································································126
Protocol-based VLAN configuration example···································································································127
IP subnet-based VLAN configuration··························································································································130
Introduction ··························································································································································130
Configuring an IP subnet-based VLAN··············································································································130
IP subnet-based VLAN configuration example ·································································································131
Displaying and maintaining VLAN ····························································································································133
Isolate-user-VLAN configuration ····························································································································· 135
Overview·······································································································································································135
Configuring isolate-user-VLAN····································································································································135
Configuring an isolate-user-VLAN······················································································································136
Configuring secondary VLANs ··························································································································136
Associating secondary VLANs with an isolate-user-VLAN ··············································································137
Displaying and maintaining isolate-user-VLAN·········································································································138
Isolate-user-VLAN configuration example ··················································································································138
Voice VLAN configuration······································································································································ 141
Overview·······································································································································································141
OUI addresses ·····················································································································································141
Voice VLAN assignment modes·························································································································141
Security mode and normal mode of voice VLANs···························································································144
Configuring a voice VLAN··········································································································································144
Configuration prerequisites ································································································································144
Configuring QoS priority settings for voice traffic on an interface································································145
Configuring a port to operate in automatic voice VLAN assignment mode ·················································145
Configuring a port to operate in manual voice VLAN assignment mode ·····················································146
Displaying and maintaining voice VLAN ··················································································································147
Voice VLAN configuration examples ·························································································································147
Automatic voice VLAN mode configuration example ·····················································································147
Manual voice VLAN assignment mode configuration example ·····································································149
GVRP configuration················································································································································· 152
Introduction to GVRP····················································································································································152
GARP ····································································································································································152
GVRP·····································································································································································155
Protocols and standards ·····································································································································155
GVRP configuration task list········································································································································156
Configuring GVRP functions········································································································································156
Configuring the GARP timers······································································································································157
Displaying and maintaining GVRP·····························································································································158
GVRP configuration examples ····································································································································158
GVRP normal registration mode configuration example·················································································158
GVRP fixed registration mode configuration example ····················································································160
GVRP forbidden registration mode configuration example············································································161

v
QinQ configuration················································································································································· 163
Introduction to QinQ····················································································································································163
Background and benefits····································································································································163
How QinQ works················································································································································163
QinQ frame structure ··········································································································································164
Implementations of QinQ ···································································································································165
Modifying the TPID in a VLAN tag····················································································································165
Protocols and standards ·····································································································································166
QinQ configuration task list········································································································································167
Configuring basic QinQ ·············································································································································167
Enabling basic QinQ··········································································································································167
Configuring VLAN transparent transmission ····································································································167
Configuring selective QinQ ········································································································································168
Configuring an outer VLAN tagging policy ·····································································································168
Configuring an inner-outer VLAN 802.1p priority mapping··········································································169
Configuring the TPID value in VLAN tags··················································································································170
QinQ configuration examples ····································································································································170
Basic QinQ configuration example···················································································································170
Selective QinQ configuration example·············································································································173
LLDP configuration··················································································································································· 176
Overview·······································································································································································176
Background··························································································································································176
Basic concepts ·····················································································································································176
How LLDP works ··················································································································································180
Protocols and standards ·····································································································································181
LLDP configuration task list ··········································································································································181
Performing basic LLDP configuration··························································································································181
Enabling LLDP ······················································································································································181
Setting the LLDP operating mode ·······················································································································182
Setting the LLDP re-initialization delay···············································································································182
Enabling LLDP polling··········································································································································183
Configuring the advertisable TLVs ·····················································································································183
Configuring the management address and its encoding format····································································183
Setting other LLDP parameters····························································································································184
Setting an encapsulation format for LLDPDUs···································································································185
Configuring CDP compatibility···································································································································185
Configuration prerequisites ································································································································186
Configuring CDP compatibility ··························································································································186
Configuring LLDP trapping ··········································································································································187
Displaying and maintaining LLDP·······························································································································187
LLDP configuration examples ······································································································································188
Basic LLDP configuration example·····················································································································188
CDP-compatible LLDP configuration example···································································································190
Index ········································································································································································ 193

1
Ethernet interface configuration
Ethernet interface naming conventions
The GE and 10-GE interfaces on the S5120-EI switches are named in the format of interface-type A/B/C,
where the following definitions apply:
•A represents the ID of the switch in an IRF fabric. If the switch is not assigned to any IRF fabric, A
uses 1.
•B represents a slot number on the switch. It uses 0 for fixed interfaces, 1 for interfaces on interface
expansion card 1, and 2 for interfaces on interface expansion card 2.
•C represents the number of an interface on a slot.
Configuring a combo interface
Introduction to combo interfaces
A combo interface is a logical interface that comprises one optical (fiber) port and one electrical (copper)
port. The two ports share one forwarding interface, so they cannot work simultaneously. When you
enable one port, the other is automatically disabled.
The fiber combo port and cooper combo port are Ethernet interfaces. They have their own separate
interface views, in which you can activate the fiber or copper combo port and configure other port
attributes such as the interface rate and duplex mode.
Configuration prerequisites
Before you configure a combo interface, complete the following tasks:
•Use the display port combo command to identify the combo interfaces on your switch and identify
the two physical ports that compose each combo interface.
•Use the display interface command to determine, of the two physical ports that compose a combo
interface, which is the fiber combo port and which is the copper combo port. If the current port is
the copper port, the output will include “Media type is twisted pair, Port hardware type is
1000_BASE_T”. If the current port is the fiber port, the output will not include the information
mentioned beforeabove. include “Media type is not sure, Port hardware type is No connector”.
Changing the active port of a combo interface
Follow these steps to change the active port of a double combo interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface
view
interface interface-type
interface-number —

2
To do… Use the command… Remarks
Activate the current
interface undo shutdown
Optional
By default, of the two ports that compose a combo
interface, the one with a smaller port ID is active.
Configuring basic settings of an Ethernet interface
You can set an Ethernet interface to operate in one of the following duplex modes:
•Full-duplex mode (full)—Interfaces that operate in this mode can send and receive packets
simultaneously.
•Half-duplex mode (half)—Interfaces that operate in this mode cannot send and receive packets
simultaneously.
•Auto-negotiation mode (auto)—Interfaces that operate in this mode negotiate a duplex mode with
their peers.
You can set the speed of an Ethernet interface or enable it to automatically negotiate a speed with its
peer. For a 100-Mbps or 1000-Mbps Ethernet interface, you can also set speed options for auto
negotiation. The two ends can select a speed only from the available options. For more information, see
“Setting speed options for auto negotiation on an Ethernet interface”
Follow these steps to configure an Ethernet interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface
view
interface interface-type
interface-number —
Set the interface
description description text
Optional
By default, the description of an interface is in the format
of interface-name Interface. For example,
GigabitEthernet1/0/1 Interface.
Set the duplex mode of
the interface
duplex { auto | full |
half }
Optional
By default, the duplex mode is auto for Ethernet
interfaces.
The half keyword is not applicable to Ethernet copper
ports that are configured with a 1000-Mbps port speed
and fiber ports.
Set the port speed speed { 10 | 100 |1000
|auto }
Optional
By default, an Ethernet interface automatically
negotiates a speed with the peer.
The 10 and 100 keywords are not applicable to 10-GE
fiber ports.
Restore the default
settings for the interface default Optional

3
NOTE:
Make sure that the fiber port speed matches the speed requirement of the inserted transceiver module. For
example, after you insert a 1000-Mbps transceiver module into a fiber port, confi
g
ure the port speed with
the speed 1000 or speed auto command.
Shutting down an Ethernet interface
You might need to shut down and then bring up an Ethernet interface to activate some configuration
changes, for example, the speed or duplex mode changes.
Follow these steps to shut down an Ethernet interface or a group of Ethernet interfaces:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface
view or port group view
•Enter Ethernet interface view:
interface interface-type interface-number
•Enter port group view:
port-group manual port-group-name
Use any command.
To shut down an Ethernet interface,
enter Ethernet interface.
To shut down all Ethernet interfaces in
a port group, enter port group view.
Shut down the Ethernet
interface or interfaces shutdown Required
By default, Ethernet interfaces are up.
CAUTION:
Use this command with caution. After you manually shut down an Ethernet interface, the Ethernet interface
cannot forward packets even if it is physically connected.
Setting speed options for auto negotiation on an
Ethernet interface
Speed auto negotiation enables an Ethernet interface to negotiate with its peer for the highest speed that
both ends support by default. You can narrow down the speed option list for negotiation.

4
Figure 1 Speed auto negotiation application scenario
IP network
Server 1 Server 2 Server 3
Switch A
GE1/0/1
GE1/0/2
GE1/0/3
GE1/0/4
As shown inFigure 1, all ports on Switch A are operating in speed auto negotiation mode, with the
highest speed of 1000 Mbps. If the transmission rate of each server in the server cluster is 1000 Mbps,
their total transmission rate will exceed the capability of port GigabitEthernet 1/0/4, the port providing
access to the Internet for the servers.
To avoid congestion on GigabitEthernet 1/0/4, set 100 Mbps as the only option available for speed
negotiation on port GigabitEthernet 1/0/1, GigabitEthernet 1/0/2, and GigabitEthernet 1/0/3. As a
result, the transmission rate on each port connected to a server is limited to 100 Mbps.
Follow these steps to set speed options for auto negotiation on an Ethernet interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view interface interface-type interface-number —
Set speed options for auto negotiation speed auto { 10 | 100 | 1000 } * Optional
NOTE:
•This function is available only for copper GE ports that support speed auto negotiation.
•The speed and speed auto commands supersede each other, and whichever is configured last takes
effect.
Configuring flow control on an Ethernet interface
To avoid packet drops on a link, you can enable flow control at both ends of the link. When traffic
congestion occurs at the receiving end, the receiving end sends a flow control (Pause) frame to ask the
sending end to suspend sending packets
•With the flow-control command configured, an interface can both send and receive flow control
frames: When congested, the interface sends a flow control frame to its peer. Upon receiving a flow
control frame from the peer, the interface suspends sending packets.
•With the flow-control receive enable command configured, an interface can receive, but not send
flow control frames. When the interface receives a flow control frame from its peer, it suspends
sending packets to the peer. When congested, the interface cannot send flow control frames to the
peer.

5
To handle unidirectional traffic congestion on a link, configure the flow-control receive enable command
at one end, and the flow-control command at the other. To enable both ends of the link to handle traffic
congestion, configure the flow-control command at both ends.
Follow these steps to enable flow control on an Ethernet interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view interface interface-type
interface-number —
Enable flow control
•Enable TxRx flow control:
flow-control
•Enable Rx flow control:
flow-control receive enable
Required
Use either command.
By default, Rx flow control is disabled
on an Ethernet interface.
Configuring link change suppression on an Ethernet
interface
An Ethernet interface has two physical link states: up and down. Each time the physical link of an
interface goes up or comes down, the physical layer reports the change to the upper layers, and the
upper layers handle the change, resulting in increased overhead.
To prevent physical link flapping from affecting system performance, configure link change suppression
to delay the reporting of physical link state changes. When the delay expires, the interface reports any
detected change.
Link change suppression does not suppress administrative up or down events. When you shut down or
bring up an interface by using the shutdown or undo shutdown command, the interface reports the event
to the upper layers immediately.
Link-down event suppression enables an interface to suppress link-down events and start a delay timer
each time the physical link goes down. During this delay, the interface does not report the link-down
event, and the display interface brief or display interface command displays the interface state as UP. If
the physical link is still down when the timer expires, the interface reports the link-down event to the upper
layers.
Link-up event suppression enables an interface to suppress link-up events and start a delay timer each
time the physical link goes up. During this delay, the interface does not report the link-up event, and the
display interface brief or display interface command displays the interface state as DOWN. If the
physical link is still up when the timer expires, the interface reports the link-up event to the upper layers.
Configuring link-down event suppression
Follow these steps to enable an Ethernet interface to suppress link-down events:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view interface interface-type
interface-number —

6
To do… Use the command… Remarks
Set a link-down event
suppression interval link-delay delay-time
Required
Link-down event suppression is disabled by
default.
Configuring link-up event suppression
Follow these steps to configure link-up event suppression on an Ethernet interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view interface interface-type
interface-number —
Set a link-up event
suppression interval link-delay delay-time mode up
Required
Link-up event suppression is disabled by
default.
NOTE:
The link-delay mode up command and the link-delay
command supersedes each other, and whichever is
configured last takes effect.
Configuring loopback testing on an Ethernet
interface
If an Ethernet interface does not work normally, you can enable loopback testing on it to identify the
problem. Loopback testing has the following types:
•Internal loopback testing—Tests all on-chip functions related to Ethernet interfaces.
•External loopback testing—Tests hardware of Ethernet interfaces. To perform external loopback
testing on an Ethernet interface, connect a loopback plug to the Ethernet interface. The switch sends
test packets out the interface, which are expected to loop over the plug and back to the interface.
If the interface fails to receive any test packet, the hardware of the interface is faulty.
An Ethernet interface in a loopback test does not forward data traffic.
Follow these steps to enable loopback testing on an Ethernet interface:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view interface interface-type
interface-number —
Enable loopback testing loopback { external | internal } Optional
Disabled by default.

7
NOTE:
•On an interface that is physically down, you can only perform internal loopback testing. On an interface
administratively shut down, you can perform neither internal nor external loopback testing.
•The speed, duplex, mdi, and shutdown commands are not available during loopback testing.
•During loopback testing, the Ethernet interface operates in full duplex mode. When you disable
loopback testing, the interface returns to its duplex setting.
•Loopback testing is a one-time operation, and is not recorded in the configuration file.
Configuring jumbo frame support
An Ethernet interface might receive some frames larger than the standard Ethernet frame size (called
"jumbo frames") during high-throughput data exchanges such as file transfers. Usually, an Ethernet
interface discards jumbo frames. With jumbo frame support enabled, the interface can process frames
larger than the standard Ethernet frame size yet within the specified range.
In interface configuration mode (Ethernet interface view or port group view), you can set the length of
jumbo frames that are allowed to pass through the Ethernet interface.
•If you execute the command in Ethernet interface view, the configuration takes effect only on the
interface.
•If you execute the command in port group view, the configuration takes effect on all ports in the port
group.
Follow these steps to configure jumbo frame support in interface view or port group view:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface
view
interface interface-type
interface-number —
Configure jumbo frame
support jumboframe enable [ value ]
Required
By default, the switch allows jumbo frames within
9216 bytes to pass through Ethernet interfaces.
If you set the value argument multiple times, the
latest configuration takes effect.
Configuring a port group
Some interfaces on your switch might use the same set of settings. To configure these interfaces in bulk
rather than one by one, you can assign them to a port group.
You create port groups manually. All settings made for a port group apply to all the member ports of the
group.
Even though the settings are made on the port group, they are saved on each interface basis rather than
on a port group basis. You can only view the settings in the view of each interface by using the display
current-configuration or display this command.
Follow these steps to configure a manual port group:

8
To do… Use the command… Remarks
Enter system view system-view —
Create a manual port group and
enter manual port group view
port-group manual
port-group-name Required
Assign Ethernet interfaces to the
manual port group
group-member
interface-list
Required
If you use the group-member interface-type
interface-start-number to interface-type
interface-end-number command to add multiple
ports in batch to the specified port group, make
sure that the interface-end-number argument
must be greater than the interface-start-number
argument.
Enabling energy saving functions on an Ethernet
interface
Enabling auto power-down
With the auto power-down function, the system automatically stops supplying power to an interface and
the interface enters the power save mode if the interface is in down state for a certain period of time
(which depends on the chip specifications and is not configurable). When the interface goes up, the
system supplies power to the interface and the interface enters its normal state.
Follow these steps to enable auto power-down:
To do… Use the command… Remarks
Enter system view system-view —
Enter Ethernet interface view or
port group view
•Enter Ethernet interface view
interface interface-type
interface-number
•Enter port group view
port-group manual
port-group-name
Use either command.
To enable auto power-down on an
Ethernet interface, enter Ethernet
interface view.
To enable auto power-down on a
group of Ethernet interfaces, enter
port group view.
Enable auto power-down port auto-power-down Required
Disabled by default.
NOTE:
When you connect an interface enabled with auto power-down to a device, if the link cannot go up
properly, disable auto power-down on the interface and try again.