Chapter 1. Using the Command-Line Interface

Information About Using the Command-Line Interface

Command Modes

Using the Help System

Understanding Abbreviated Commands

No and Default Forms of Commands

CLI Error Messages

Configuration Logging

Configuring the Command History

Changing the Command History Buffer Size

Recalling Commands

Disabling the Command History Feature

Enabling and Disabling Editing Features

Editing Commands Through Keystrokes

Editing Command Lines That Wrap

Searching and Filtering Output of show and more Commands

Accessing the CLI Through a Console Connection or Through Telnet

Chapter 2. Configuring EtherChannels and Link-State Tracking

Finding Feature Information

Restrictions for EtherChannels

Information About EtherChannels

EtherChannel Overview

EtherChannel Modes

EtherChannel on Controllers

EtherChannel Link Failover

Channel Groups and Port-Channel Interfaces

Port Aggregation Protocol

PAgP Modes

Silent Mode

PAgP Learn Method and Priority

PAgP Interaction with Other Features

Link Aggregation Control Protocol

LACP Modes

LACP and Link Redundancy

LACP Interaction with Other Features

EtherChannel On Mode

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

EtherChannel and Controller Stacks

Controller Stack and PAgP

Controller Stacks and LACP

Default EtherChannel Configuration

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Layer 3 EtherChannel Configuration Guidelines

How to Configure EtherChannels

Configuring Layer 2 EtherChannels (CLI)

Configuring Layer 3 EtherChannels (CLI)

Configuring EtherChannel Load-Balancing (CLI)

Configuring EtherChannel Extended Load-Balancing (CLI)

Configuring the PAgP Learn Method and Priority (CLI)

Configuring LACP Hot-Standby Ports

Configuring the LACP Max Bundle Feature (CLI)

Configuring the Port Channel Min-Links Feature (CLI)

Configuring the LACP System Priority (CLI)

Configuring the LACP Port Priority (CLI)

Monitoring EtherChannel, PAgP, and LACP Status

Configuration Examples for Configuring EtherChannels

Configuring Layer 2 EtherChannels: Examples

Configuring Layer 3 EtherChannels: Examples

Configuring LACP Hot-Standby Ports: Example

Additional References for EtherChannels

Feature Information for EtherChannels

Chapter 3. Configuring Flex Links and the MAC Address-Table Move Update Feature

Finding Feature Information

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Information About Flex Links and MAC Address-Table Move Update

Flex Links

Flex Links Configuration

VLAN Flex Links Load Balancing and Support

Multicast Fast Convergence with Flex Links Failover

Learning the Other Flex Links Port as the mrouter Port

Generating IGMP Reports

Leaking IGMP Reports

MAC Address-Table Move Update

Flex Links VLAN Load Balancing Configuration Guidelines

MAC Address-Table Move Update Configuration Guidelines

Default Flex Links and MAC Address-Table Move Update Configuration

How to Configure Flex Links and the MAC Address-Table Move Update Feature

Configuring Flex Links (CLI)

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring VLAN Load Balancing on Flex Links (CLI)

Configuring MAC Address-Table Move Update (CLI)

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuration Examples for Flex Links

Configuring Flex Links: Examples

Configuring VLAN Load Balancing on Flex Links: Examples

Configuring the MAC Address-Table Move Update: Examples

Configuring Multicast Fast Convergence with Flex Links Failover: Examples

Additional References for Flex Links and MAC Address-Table Move Update

Feature Information for Flex Links and MAC Address-Table Move Update

Chapter 4. Configuring UniDirectional Link Detection

Finding Feature Information

Restrictions for Configuring UDLD

Information About UDLD

Modes of Operation

Normal Mode

Aggressive Mode

Methods to Detect Unidirectional Links

Neighbor Database Maintenance

Event-Driven Detection and Echoing

UDLD Reset Options

Default UDLD Configuration

How to Configure UDLD

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Monitoring and Maintaining UDLD

Additional References for UDLD

Feature Information for UDLD

Preface

Obtaining Documentation and Submitting a Service Request

Document Conventions

Related Documentation

Copyright Page

Chapter 1. Using the Command-Line Interface

- Information About Using the Command-Line Interface

Information About Using the Command-Line Interface

- Command Modes

- Using the Help System

- Understanding Abbreviated Commands

- No and Default Forms of Commands

- CLI Error Messages

- Configuration Logging

Command Modes

The Cisco IOS user interface is divided into many different modes. The commands available to you depend on which mode you are currently in. Enter a question mark (?) at the system prompt to obtain a list of commands available for each command mode.

You can start a CLI session through a console connection, through Telnet, a SSH, or by using the browser.

When you start a session, you begin in user mode, often called user EXEC mode. Only a limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC commands are one-time commands, such as show commands, which show the current configuration status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved when the controller reboots.

To have access to all commands, you must enter privileged EXEC mode. Normally, you must enter a password to enter privileged EXEC mode. From this mode, you can enter any privileged EXEC command or enter global configuration mode.

Using the configuration modes (global, interface, and line), you can make changes to the running configuration. If you save the configuration, these commands are stored and used when the controller reboots. To access the various configuration modes, you must start at global configuration mode. From global configuration mode, you can enter interface configuration mode and line configuration mode.

This table describes the main command modes, how to access each one, the prompt you see in that mode, and how to exit the mode.

Command Mode Summary

Mode

Access Method

Prompt

Exit Method

About This Mode

User EXEC

Begin a session using Telnet, SSH, or console.

Controller>

Enter logout or quit.

Use this mode to

- Change terminal settings.

- Perform basic tests.

- Display system information.

Privileged EXEC

While in user EXEC mode, enter the enable command.

Controller#

Enter disable to exit.

Use this mode to verify commands that you have entered. Use a password to protect access to this mode.

Use this mode to execute privilege EXEC commands for access points. These commands are not part of the running config of the controller, they are sent to the IOS config of the access point.

Global configuration

While in privileged EXEC mode, enter the configure command.

Controller(config)#

To exit to privileged EXEC mode, enter exit or end, or press Ctrl-Z.

Use this mode to configure parameters that apply to the entire controller.

Use this mode to configure access point commands that are part of the running config of the controller.

VLAN configuration

While in global configuration mode, enter the vlan vlan-id command.

Controller(config-vlan)#

To exit to global configuration mode, enter the exit command.

To return to privileged EXEC mode, press Ctrl-Z or enter end.

Use this mode to configure VLAN parameters. When VTP mode is transparent, you can create extended-range VLANs (VLAN IDs greater than 1005) and save configurations in the controller startup configuration file.

Interface configuration

While in global configuration mode, enter the interface command (with a specific interface).

Controller(config-if)#

To exit to global configuration mode, enter exit.

To return to privileged EXEC mode, press Ctrl-Z or enter end.

Use this mode to configure parameters for the Ethernet ports.

Line configuration

While in global configuration mode, specify a line with the line vty or line console command.

Controller(config-line)#

To exit to global configuration mode, enter exit.

To return to privileged EXEC mode, press Ctrl-Z or enter end.

Use this mode to configure parameters for the terminal line.

Using the Help System

You can enter a question mark (?) at the system prompt to display a list of commands available for each command mode. You can also obtain a list of associated keywords and arguments for any command.

SUMMARY STEPS

1.    help

2.    abbreviated-command-entry ?

3.    abbreviated-command-entry <Tab>

4.    ?

5.    command ?

6.    command keyword ?

DETAILED STEPS

Command or Action

Purpose

Step 1

help

Example:

Controller# help

Obtains a brief description of the help system in any command mode.

Step 2

abbreviated-command-entry ?

Example:

Controller# di?
dir disable disconnect

Obtains a list of commands that begin with a particular character string.

Step 3

abbreviated-command-entry <Tab>

Example:

Controller# sh conf<tab>
Controller# show configuration

Completes a partial command name.

Step 4

?

Example:

Controller> ?

Lists all commands available for a particular command mode.

Step 5

command ?

Example:

Controller> show ?

Lists the associated keywords for a command.

Step 6

command keyword ?

Example:

Controller(config)# cdp holdtime ?
<10-255> Length of time (in sec) that receiver must keep this packet

Lists the associated arguments for a keyword.

Understanding Abbreviated Commands

You need to enter only enough characters for the controller to recognize the command as unique.

This example shows how to enter the show configuration privileged EXEC command in an abbreviated form:

Controller# show conf

No and Default Forms of Commands

Almost every configuration command also has a no form. In general, use the no form to disable a feature or function or reverse the action of a command. For example, the no shutdown interface configuration command reverses the shutdown of an interface. Use the command without the keyword no to reenable a disabled feature or to enable a feature that is disabled by default.

Configuration commands can also have a default form. The default form of a command returns the command setting to its default. Most commands are disabled by default, so the default form is the same as the no form. However, some commands are enabled by default and have variables set to certain default values. In these cases, the default command enables the command and sets variables to their default values.

CLI Error Messages

This table lists some error messages that you might encounter while using the CLI to configure your controller.

Common CLI Error Messages

Error Message

Meaning

How to Get Help

% Ambiguous command: "show con"

You did not enter enough characters for your controller to recognize the command.

Reenter the command followed by a question mark (?) without any space between the command and the question mark.

The possible keywords that you can enter with the command appear.

% Incomplete command.

You did not enter all of the keywords or values required by this command.

Reenter the command followed by a question mark (?) with a space between the command and the question mark.

The possible keywords that you can enter with the command appear.

% Invalid input detected at ‘^’ marker.

You entered the command incorrectly. The caret (^) marks the point of the error.

Enter a question mark (?) to display all of the commands that are available in this command mode.

The possible keywords that you can enter with the command appear.

Configuration Logging

You can log and view changes to the controller configuration. You can use the Configuration Change Logging and Notification feature to track changes on a per-session and per-user basis. The logger tracks each configuration command that is applied, the user who entered the command, the time that the command was entered, and the parser return code for the command. This feature includes a mechanism for asynchronous notification to registered applications whenever the configuration changes. You can choose to have the notifications sent to the syslog.

Note

Only CLI or HTTP changes are logged.

Configuring the Command History

The software provides a history or record of commands that you have entered. The command history feature is particularly useful for recalling long or complex commands or entries, including access lists. You can customize this feature to suit your needs.

- Changing the Command History Buffer Size

- Recalling Commands

- Disabling the Command History Feature

Changing the Command History Buffer Size

By default, the controller records ten command lines in its history buffer. You can alter this number for a current terminal session or for all sessions on a particular line. This procedure is optional.

SUMMARY STEPS

1.    terminal history [size number-of-lines]

DETAILED STEPS

Command or Action

Purpose

Step 1

terminal history [size number-of-lines]

Example:

Controller# terminal history size 200

Changes the number of command lines that the controller records during the current terminal session in privileged EXEC mode. You can configure the size from 0 to 256.

Recalling Commands

To recall commands from the history buffer, perform one of the actions listed in this table. These actions are optional.

Note

The arrow keys function only on ANSI-compatible terminals such as VT100s.

SUMMARY STEPS

1.    Ctrl-P or use the up arrow key

2.    Ctrl-N or use the down arrow key

3.    show history

DETAILED STEPS

Command or Action

Purpose

Step 1

Ctrl-P or use the up arrow key

Recalls commands in the history buffer, beginning with the most recent command. Repeat the key sequence to recall successively older commands.

Step 2

Ctrl-N or use the down arrow key

Returns to more recent commands in the history buffer after recalling commands with Ctrl-P or the up arrow key. Repeat the key sequence to recall successively more recent commands.

Step 3

show history

Example:

Controller# show history

Lists the last several commands that you just entered in privileged EXEC mode. The number of commands that appear is controlled by the setting of the terminal history global configuration command and the history line configuration command.

Disabling the Command History Feature

The command history feature is automatically enabled. You can disable it for the current terminal session or for the command line. This procedure is optional.

SUMMARY STEPS

1.    terminal no history

DETAILED STEPS

Command or Action

Purpose

Step 1

terminal no history

Example:

Controller# terminal no history

Disables the feature during the current terminal session in privileged EXEC mode.

Enabling and Disabling Editing Features

Although enhanced editing mode is automatically enabled, you can disable it and reenable it.

SUMMARY STEPS

1.    terminal editing

2.    terminal no editing

DETAILED STEPS

Command or Action

Purpose

Step 1

terminal editing

Example:

Controller# terminal editing

Reenables the enhanced editing mode for the current terminal session in privileged EXEC mode.

Step 2

terminal no editing

Example:

Controller# terminal no editing

Disables the enhanced editing mode for the current terminal session in privileged EXEC mode.

- Editing Commands Through Keystrokes

- Editing Command Lines That Wrap

Editing Commands Through Keystrokes

The keystrokes help you to edit the command lines. These keystrokes are optional.

Note

The arrow keys function only on ANSI-compatible terminals such as VT100s.

Editing Commands

Editing Commands

Description

Ctrl-B or use the left arrow key

Moves the cursor back one character.

Ctrl-F or use the right arrow key

Moves the cursor forward one character.

Ctrl-A

Moves the cursor to the beginning of the command line.

Ctrl-E

Moves the cursor to the end of the command line.

Esc B

Moves the cursor back one word.

Esc F

Moves the cursor forward one word.

Ctrl-T

Transposes the character to the left of the cursor with the character located at the cursor.

Delete or Backspace key

Erases the character to the left of the cursor.

Ctrl-D

Deletes the character at the cursor.

Ctrl-K

Deletes all characters from the cursor to the end of the command line.

Ctrl-U or Ctrl-X

Deletes all characters from the cursor to the beginning of the command line.

Ctrl-W

Deletes the word to the left of the cursor.

Esc D

Deletes from the cursor to the end of the word.

Esc C

Capitalizes at the cursor.

Esc L

Changes the word at the cursor to lowercase.

Esc U

Capitalizes letters from the cursor to the end of the word.

Ctrl-V or Esc Q

Designates a particular keystroke as an executable command, perhaps as a shortcut.

Return key

Scrolls down a line or screen on displays that are longer than the terminal screen can display.

Note:
The More prompt is used for any output that has more lines than can be displayed on the terminal screen, including show command output. You can use the Return and Space bar keystrokes whenever you see the More prompt.

Space bar

Scrolls down one screen.

Ctrl-L or Ctrl-R

Redisplays the current command line if the controller suddenly sends a message to your screen.

Editing Command Lines That Wrap

You can use a wraparound feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. You cannot see the first ten characters of the line, but you can scroll back and check the syntax at the beginning of the command. The keystroke actions are optional.

To scroll back to the beginning of the command entry, press Ctrl-B or the left arrow key repeatedly. You can also press Ctrl-A to immediately move to the beginning of the line.

Note

The arrow keys function only on ANSI-compatible terminals such as VT100s.

The following example shows how to wrap a command line that extends beyond a single line on the screen.

SUMMARY STEPS

1.    access-list

2.    Ctrl-A

3.    Return key

DETAILED STEPS

Command or Action

Purpose

Step 1

access-list

Example:

Controller(config)# access-list 101 permit tcp 10.15.22.25 255.255.255.0 10.15.22.35
Controller(config)# $ 101 permit tcp 10.15.22.25 255.255.255.0 10.15.22.35 255.25
Controller(config)# $t tcp 10.15.22.25 255.255.255.0 131.108.1.20 255.255.255.0 eq
Controller(config)# $15.22.25 255.255.255.0 10.15.22.35 255.255.255.0 eq 45

Displays the global configuration command entry that extends beyond one line.

When the cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar sign ($) shows that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted ten spaces to the left.

Step 2

Ctrl-A

Example:

Controller(config)# access-list 101 permit tcp 10.15.22.25 255.255.255.0 10.15.2$

Checks the complete syntax.

The dollar sign ($) appears at the end of the line to show that the line has been scrolled to the right.

Step 3

Return key

Execute the commands.

The software assumes that you have a terminal screen that is 80 columns wide. If you have a different width, use the terminal width privileged EXEC command to set the width of your terminal.

Use line wrapping with the command history feature to recall and modify previous complex command entries.

Searching and Filtering Output of show and more Commands

You can search and filter the output for show and more commands. This is useful when you need to sort through large amounts of output or if you want to exclude output that you do not need to see. Using these commands is optional.

SUMMARY STEPS

1.    {show | more} command | {begin | include | exclude} regular-expression

DETAILED STEPS

Command or Action

Purpose

Step 1

{show | more} command | {begin | include | exclude} regular-expression

Example:

Controller# show interfaces | include protocol
Vlan1 is up, line protocol is up
Vlan10 is up, line protocol is down
GigabitEthernet1/0/1 is up, line protocol is down
GigabitEthernet1/0/2 is up, line protocol is up

Searches and filters the output.

Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output are not displayed, but the lines that contain output appear.

Accessing the CLI Through a Console Connection or Through Telnet

Before you can access the CLI, you must connect a terminal or a PC to the controller console or connect a PC to the Ethernet management port and then power on the controller, as described in the hardware installation guide that shipped with your controller.

If your controller is already configured, you can access the CLI through a local console connection or through a remote Telnet session, but your controller must first be configured for this type of access.

You can use one of these methods to establish a connection with the controller:

- Connect the controller console port to a management station or dial-up modem, or connect the Ethernet management port to a PC. For information about connecting to the console or Ethernet management port, see the controller hardware installation guide.

- Use any Telnet TCP/IP or encrypted Secure Shell (SSH) package from a remote management station. The controller must have network connectivity with the Telnet or SSH client, and the controller must have an enable secret password configured.

- The controller supports up to 16 simultaneous Telnet sessions. Changes made by one Telnet user are reflected in all other Telnet sessions.

- The controller supports up to five simultaneous secure SSH sessions.

After you connect through the console port, through the Ethernet management port, through a Telnet session or through an SSH session, the user EXEC prompt appears on the management station.

Chapter 2. Configuring EtherChannels and Link-State Tracking

- Finding Feature Information

- Restrictions for EtherChannels

- Information About EtherChannels

- How to Configure EtherChannels

- Monitoring EtherChannel, PAgP, and LACP Status

- Configuration Examples for Configuring EtherChannels

- Additional References for EtherChannels

- Feature Information for EtherChannels

Finding Feature Information

IEEE 802.1x port-based authentication prevents unauthorized devices (clients) from gaining access to the network. Unless otherwise noted, the term switch refers to a standalone switch and to a switch stack.

Note

Stacking is supported only on Catalyst 2960-S switches running the LAN base image.

Restrictions for EtherChannels

The following are restrictions for EtherChannels:

- All ports in an EtherChannel must be assigned to the same VLAN or they must be configured as trunk ports.

- Layer 3 EtherChannels are not supported if running the LAN Base license feature set.

Information About EtherChannels

- EtherChannel Overview

- Channel Groups and Port-Channel Interfaces

- Port Aggregation Protocol

- Link Aggregation Control Protocol

- EtherChannel On Mode

- Load-Balancing and Forwarding Methods

- EtherChannel and Controller Stacks

- Default EtherChannel Configuration

- EtherChannel Configuration Guidelines

EtherChannel Overview

EtherChannel provides fault-tolerant high-speed links between switches, routers, and servers. You can use the EtherChannel to increase the bandwidth between the wiring closets and the data center, and you can deploy it anywhere in the network where bottlenecks are likely to occur. EtherChannel provides automatic recovery for the loss of a link by redistributing the load across the remaining links. If a link fails, EtherChannel redirects traffic from the failed link to the remaining links in the channel without intervention.

An EtherChannel consists of individual Ethernet links bundled into a single logical link.

Typical EtherChannel Configuration

The EtherChannel provides full-duplex bandwidth up to 8 Gb/s (Gigabit EtherChannel) or 80 Gb/s (10-Gigabit EtherChannel) between your switch and another switch or host.

Each EtherChannel can consist of up to eight compatibly configured Ethernet ports.

The number of EtherChannels is limited to 128.

All ports in each EtherChannel must be configured as either Layer 2 or Layer 3 ports. The EtherChannel Layer 3 ports are made up of routed ports. Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface configuration command.

- EtherChannel Modes

- EtherChannel on Controllers

- EtherChannel Link Failover

EtherChannel Modes

You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), or On. Configure both ends of the EtherChannel in the same mode:

- When you configure one end of an EtherChannel in either PAgP or LACP mode, the system negotiates with the other end of the channel to determine which ports should become active. If the remote port cannot negotiate an EtherChannel, the local port is put into an independent state and continues to carry data traffic as would any other single link. The port configuration does not change, but the port does not participate in the EtherChannel.

- When you configure an EtherChannel in the on mode, no negotiations take place. The switch forces all compatible ports to become active in the EtherChannel. The other end of the channel (on the other switch) must also be configured in the on mode; otherwise, packet loss can occur.

EtherChannel on Controllers

You can create an EtherChannel on a controller, on a single controller in the stack, or on multiple controllers in the stack (known as cross-stack EtherChannel).

Single Controller EtherChannel

This figure shows the recommended cross-stack EtherChannel configuration with three active links and three standby links.

Cross-Stack EtherChannel

EtherChannel Link Failover

If a link within an EtherChannel fails, traffic previously carried over that failed link moves to the remaining links within the EtherChannel. If traps are enabled on the switch, a trap is sent for a failure that identifies the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast packets on one link in an EtherChannel are blocked from returning on any other link of the EtherChannel.

Channel Groups and Port-Channel Interfaces

An EtherChannel comprises a channel group and a port-channel interface. The channel group binds physical ports to the port-channel interface. Configuration changes applied to the port-channel interface apply to all the physical ports bound together in the channel group.

Relationship of Physical Ports, Channel Group and Port-Channel Interface.
The channel-group command binds the physical port and the port-channel interface together. Each EtherChannel has a port-channel logical interface numbered from 1 to 128. This port-channel interface number corresponds to the one specified with the channel-group interface configuration command.

- With Layer 2 ports, use the channel-group interface configuration command to dynamically create the port-channel interface. You also can use the interface port-channel port-channel-number global configuration command to manually create the port-channel interface, but then you must use the channel-group channel-group-number command to bind the logical interface to a physical port. The channel-group-number can be the same as the port-channel-number, or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.

- With Layer 3 ports, you should manually create the logical interface by using the interface port-channel global configuration command followed by the no switchport interface configuration command. You then manually assign an interface to the EtherChannel by using the channel-group interface configuration command.

Port Aggregation Protocol

The Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that can be run only on Cisco controllers and on those controllers licensed by vendors to support PAgP. PAgP facilitates the automatic creation of EtherChannels by exchanging PAgP packets between Ethernet ports.

By using PAgP, the controller or controller stack learns the identity of partners capable of supporting PAgP and the capabilities of each port. It then dynamically groups similarly configured ports (on a single controller in the stack) into a single logical link (channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and port parameter constraints. For example, PAgP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single controller port.

- PAgP Modes

- PAgP Learn Method and Priority

- PAgP Interaction with Other Features

PAgP Modes

PAgP modes specify whether a port can send PAgP packets, which start PAgP negotiations, or only respond to PAgP packets received.

EtherChannel PAgP Modes

Mode

Description

auto

Places a port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

desirable

Places a port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets.

Switch ports exchange PAgP packets only with partner ports configured in the auto or desirable modes. Ports configured in the on mode do not exchange PAgP packets.

Both the auto and desirable modes enable ports to negotiate with partner ports to form an EtherChannel based on criteria such as port speed. and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:

- A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

- A port in the auto mode can form an EtherChannel with another port in the desirable mode.

A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.

- Silent Mode

Silent Mode

If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.

Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

PAgP Learn Method and Priority

Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a physical learner if it learns addresses by physical ports and directs transmissions based on that knowledge. A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports. The learn method must be configured the same at both ends of the link.

When a device and its partner are both aggregate-port learners, they learn the address on the logical port-channel. The device sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives.

PAgP cannot automatically detect when the partner device is a physical learner and when the local device is an aggregate-port learner. Therefore, you must manually set the learning method on the local device to learn addresses by physical ports. You also must set the load-distribution method to source-based distribution, so that any given source MAC address is always sent on the same physical port.

You also can configure a single port within the group for all transmissions and use other ports for hot-standby. The unused ports in the group can be swapped into operation in just a few seconds if the selected single port loses hardware-signal detection. You can configure which port is always selected for packet transmission by changing its priority with the pagp port-priority interface configuration command. The higher the priority, the more likely that the port will be selected.

Note

The controller supports address learning only on aggregate ports even though the physical-port keyword is provided in the CLI. The pagp learn-method command and the pagp port-priority command have no effect on the controller hardware, but they are required for PAgP interoperability with devices that only support address learning by physical ports, such as the Catalyst 1900 switch.

When the link partner of the controller is a physical learner, we recommend that you configure the controller as a physical-port learner by using the pagp learn-method physical-port interface configuration command. Set the load-distribution method based on the source MAC address by using the port-channel load-balance src-mac global configuration command. The controller then sends packets to the physcial learner using the same port in the EtherChannel from which it learned the source address. Only use the pagp learn-method command in this situation.

PAgP Interaction with Other Features

The Dynamic Trunking Protocol (DTP) and the Cisco Discovery Protocol (CDP) send and receive packets over the physical ports in the EtherChannel. Trunk ports send and receive PAgP protocol data units (PDUs) on the lowest numbered VLAN.

In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address to the EtherChannel. For Layer 3 EtherChannels, the MAC address is allocated by the active controller as soon as the interface is created (through the interface port-channel global configuration command).

PAgP sends and receives PAgP PDUs only from ports that are up and have PAgP enabled for the auto or desirable mode.

Link Aggregation Control Protocol

The LACP is defined in IEEE 802.3ad and enables Cisco controllers to manage Ethernet channels between controllers that conform to the IEEE 802.3ad protocol. LACP facilitates the automatic creation of EtherChannels by exchanging LACP packets between Ethernet ports.

By using LACP, the controller or controller stack learns the identity of partners capable of supporting LACP and the capabilities of each port. It then dynamically groups similarly configured ports into a single logical link (channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, LACP adds the group to the spanning tree as a single controller port.

- LACP Modes

- LACP and Link Redundancy

- LACP Interaction with Other Features

LACP Modes

LACP modes specify whether a port can send LACP packets or only receive LACP packets.

EtherChannel LACP Modes

Mode

Description

active

Places a port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

passive

Places a port into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation. This setting minimizes the transmission of LACP packets.

Both the active and passive LACP modes enable ports to negotiate with partner ports to an EtherChannel based on criteria such as port speed, and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different LACP modes as long as the modes are compatible. For example:

- A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.

- A port in the passive mode cannot form an EtherChannel with another port that is also in the passive mode because neither port starts LACP negotiation.

LACP and Link Redundancy

LACP port-channel operation, bandwidth availability, and link redundancy can be further refined with the LACP port-channel min-links and the LACP max-bundle features.

The LACP port-channel min-links feature:

- Configures the minimum number of ports that must be linked up and bundled in the LACP port channel.

- Prevents a low-bandwidth LACP port channel from becoming active.

- Causes an LACP port channel to become inactive if there are too few active members ports to supply the required minimum bandwidth.

The LACP max-bundle feature:

- Defines an upper limit on the number of bundled ports in an LACP port channel.

- Allows hot-standby ports with fewer bundled ports. For example, in an LACP port channel with five ports, you can specify a max-bundle of three, and the two remaining ports are designated as hot-standby ports.

LACP Interaction with Other Features

The DTP and the CDP send and receive packets over the physical ports in the EtherChannel. Trunk ports send and receive LACP PDUs on the lowest numbered VLAN.

In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides its MAC address to the EtherChannel. For Layer 3 EtherChannels, the MAC address is allocated by the active controller as soon as the interface is created through the interface port-channel global configuration command.

LACP sends and receives LACP PDUs only from ports that are up and have LACP enabled for the active or passive mode.

EtherChannel On Mode

EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port to join an EtherChannel without negotiations. The on mode can be useful if the remote device does not support PAgP or LACP. In the on mode, a usable EtherChannel exists only when the controllers at both ends of the link are configured in the on mode.

Ports that are configured in the on mode in the same channel group must have compatible port characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they are configured in the on mode.

Caution

You should use care when using the on mode. This is a manual configuration, and ports on both ends of the EtherChannel must have the same configuration. If the group is misconfigured, packet loss or spanning-tree loops can occur.

Load-Balancing and Forwarding Methods

EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel. You can specify one of several different load-balancing modes, including load distribution based on MAC addresses, IP addresses, source addresses, destination addresses, or both source and destination addresses. The selected mode applies to all EtherChannels configured on the controller.

You configure the load-balancing and forwarding method by using the port-channel load-balance and the port-channel load-balance extendedglobal configuration commands.

- MAC Address Forwarding

- IP Address Forwarding

- Load-Balancing Advantages

MAC Address Forwarding

With source-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide load-balancing, packets from different hosts use different ports in the channel, but packets from the same host use the same port in the channel.

With destination-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the destination host’s MAC address of the incoming packet. Therefore, packets to the same destination are forwarded over the same port, and packets to a different destination are sent on a different port in the channel.

With source-and-destination MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on both the source and destination MAC addresses. This forwarding method, a combination source-MAC and destination-MAC address forwarding methods of load distribution, can be used if it is not clear whether source-MAC or destination-MAC address forwarding is better suited on a particular controller. With source-and-destination MAC-address forwarding, packets sent from host A to host B, host A to host C, and host C to host B could all use different ports in the channel.

IP Address Forwarding

With source-IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on the source-IP address of the incoming packet. To provide load balancing, packets from different IP addresses use different ports in the channel, and packets from the same IP address use the same port in the channel.

With destination-IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on the destination-IP address of the incoming packet. To provide load balancing, packets from the same IP source address sent to different IP destination addresses could be sent on different ports in the channel. Packets sent from different source IP addresses to the same destination IP address are always sent on the same port in the channel.

With source-and-destination IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on both the source and destination IP addresses of the incoming packet. This forwarding method, a combination of source-IP and destination-IP address-based forwarding, can be used if it is not clear whether source-IP or destination-IP address-based forwarding is better suited on a particular controller. In this method, packets sent from the IP address A to IP address B, from IP address A to IP address C, and from IP address C to IP address B could all use different ports in the channel.

Load-Balancing Advantages

Different load-balancing methods have different advantages, and the choice of a particular load-balancing method should be based on the position of the controller in the network and the kind of traffic that needs to be load-distributed.

Load Distribution and Forwarding. In the figure below the controller does source MAC-based forwarding over the EtherChannel links and evenly distributes the traffic over multiple links of the EtherChannel.

Use the option that provides the greatest variety in your configuration. For example, if the traffic on a channel is going only to a single MAC address, using the destination-MAC address always chooses the same link in the channel. Using source addresses or IP addresses might result in better load-balancing.

EtherChannel and Controller Stacks

If a stack member that has ports participating in an EtherChannel fails or leaves the stack, the active controller removes the failed stack member controller ports from the EtherChannel. The remaining ports of the EtherChannel, if any, continue to provide connectivity.

When a controller is added to an existing stack, the new controller receives the running configuration from the active controller and updates itself with the EtherChannel-related stack configuration. The stack member also receives the operational information (the list of ports that are up and are members of a channel).

When two stacks merge that have EtherChannels configured between them, self-looped ports result. Spanning tree detects this condition and acts accordingly. Any PAgP or LACP configuration on a winning controller stack is not affected, but the PAgP or LACP configuration on the losing controller stack is lost after the stack reboots.

- Controller Stack and PAgP

- Controller Stacks and LACP

Controller Stack and PAgP

With PAgP, if the active controller fails or leaves the stack, the standby controller becomes the new active controller. The new active controller synchronizes the configuration of the stack members to that of the active controller. The PAgP configuration is not affected after an active controller change unless the EtherChannel has ports residing on the old active controller.

Controller Stacks and LACP

With LACP, the system ID uses the stack MAC address from the active controller. When an active controller fails or leaves the stack and the standby controller becomes the new active controller change, the LACP system ID is unchanged. By default, the LACP configuration is not affected after the active controller changes.

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

- Layer 2 EtherChannel Configuration Guidelines

- Layer 3 EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Layer 3 EtherChannel Configuration Guidelines

- For Layer 3 EtherChannels, assign the Layer 3 address to the port-channel logical interface, not to the physical ports in the channel.

How to Configure EtherChannels

After you configure an EtherChannel, configuration changes applied to the port-channel interface apply to all the physical ports assigned to the port-channel interface, and configuration changes applied to the physical port affect only the port where you apply the configuration.

- Configuring Layer 2 EtherChannels (CLI)

- Configuring Layer 3 EtherChannels (CLI)

- Configuring EtherChannel Load-Balancing (CLI)

- Configuring EtherChannel Extended Load-Balancing (CLI)

- Configuring the PAgP Learn Method and Priority (CLI)

- Configuring LACP Hot-Standby Ports

Configuring Layer 2 EtherChannels (CLI)

You configure Layer 2 EtherChannels by assigning ports to a channel group with the channel-group interface configuration command. This command automatically creates the port-channel logical interface.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport mode {access | trunk}

4.    switchport access vlan vlan-id

5.    channel-group channel-group-number mode {auto [non-silent] | desirable [non-silent ] | on } | { active | passive}

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters the global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet2/0/1

Specifies a physical port, and enters interface configuration mode.

Valid interfaces are physical ports.

For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group.

For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

Step 3

switchport mode {access | trunk}

Example:

Controller(config-if)# switchport mode access

Assigns all ports as static-access ports in the same VLAN, or configure them as trunks.

If you configure the port as a static-access port, assign it to only one VLAN. The range is 1 to 4094.

Step 4

switchport access vlan vlan-id

Example:

Controller(config-if)# switchport access vlan 22

(Optional) If you configure the port as a static-access port, assign it to only one VLAN. The range is 1 to 4094.

Step 5

channel-group channel-group-number mode {auto [non-silent] | desirable [non-silent ] | on } | { active | passive}

Example:

Controller(config-if)# channel-group 5 mode auto

Assigns the port to a channel group, and specifies the PAgP or the LACP mode.

For channel-group-number, the range is 1 to 128.

For mode, select one of these keywords:

- auto —Enables PAgP only if a PAgP device is detected. It places the port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation.This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- desirable —Unconditionally enables PAgP. It places the port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- on —Forces the port to channel without PAgP or LACP. In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode.

- non-silent —(Optional) If your controller is connected to a partner that is PAgP-capable, configures the controller port for nonsilent operation when the port is in the auto or desirable mode. If you do not specify non-silent, silent is assumed. The silent setting is for connections to file servers or packet analyzers. This setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

- active—Enables LACP only if a LACP device is detected. It places the port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

- passive —Enables LACP on the port and places it into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation.

Step 6

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Configuring Layer 3 EtherChannels (CLI)

Beginning in privileged EXEC mode, follow these steps to assign an Ethernet port to a Layer 3 EtherChannel. This procedure is required.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    no ip address

4.    no switchport

5.    channel-group channel-group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive }

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies a physical port, and enters interface configuration mode.

Valid interfaces include physical ports.

For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group.

For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

Step 3

no ip address

Example:

Controller(config-if)# no ip address

Ensures that there is no IP address assigned to the physical port.

Step 4

no switchport

Example:

Controller(config-if)# no switchport

Puts the port into Layer 3 mode.

Step 5

channel-group channel-group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive }

Example:

Controller(config-if)# channel-group 5 mode auto

Assigns the port to a channel group, and specifies the PAgP or the LACP mode.

For mode, select one of these keywords:

- auto—Enables PAgP only if a PAgP device is detected. It places the port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- desirable—Unconditionally enables PAgP. It places the port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- on—Forces the port to channel without PAgP or LACP. In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode.

- non-silent—(Optional) If your controller is connected to a partner that is PAgP capable, configures the controller port for nonsilent operation when the port is in the auto or desirable mode. If you do not specify non-silent, silent is assumed. The silent setting is for connections to file servers or packet analyzers. This setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

- active—Enables LACP only if a LACP device is detected. It places the port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

- passive —Enables LACP on the port and places it into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation.

Step 6

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Configuring EtherChannel Load-Balancing (CLI)

You can configure EtherChannel load-balancing to use one of several different forwarding methods.

This task is optional.

SUMMARY STEPS

1.    configure terminal

2.    port-channel load-balance { dst-ip | dst-mac | dst-mixed-ip-port | dst-port | extended [dst-ip | dst-mac | dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ] | src-dst-ip | src-dst-mac src-dst-mixed-ip-port src-dst-portsrc-ip | src-mac | src-mixed-ip-port | src-port}

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

port-channel load-balance { dst-ip | dst-mac | dst-mixed-ip-port | dst-port | extended [dst-ip | dst-mac | dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ] | src-dst-ip | src-dst-mac src-dst-mixed-ip-port src-dst-portsrc-ip | src-mac | src-mixed-ip-port | src-port}

Example:

Controller(config)# port-channel load-balance src-mac

Configures an EtherChannel load-balancing method.

The default is src-mac.

Select one of these load-distribution methods:

- dst-ip—Specifies destination-host IP address.

- dst-mac—Specifies the destination-host MAC address of the incoming packet.

- dst-mixed-ip-port—Specifies the host IP address and TCP/UDP port.

- dst-port—Specifies the destination TCP/UDP port.

- extended—Specifies extended load balance methods--combinations of source and destination methods beyond those available with the standard command.

- ipv6-label—Specifies the IPv6 flow label.

- l3-proto—Specifies the Layer 3 protocol.

- src-dst-ip—Specifies the source and destination host IP address.

- src-dst-mac—Specifies the source and destination host MAC address.

- src-dst-mixed-ip-port—Specifies the source and destination host IP address and TCP/UDP port.

- src-dst-port—Specifies the source and destination TCP/UDP port.

- src-ip—Specifies the source host IP address.

- src-mac—Specifies the source MAC address of the incoming packet.

- src-mixed-ip-port—Specifies the source host IP address and TCP/UDP port.

- src-port—Specifies the source TCP/UDP port.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Configuring EtherChannel Extended Load-Balancing (CLI)

Configure EtherChannel extended load-balancing when you want to use a combination of load-balancing methods.

This task is optional.

SUMMARY STEPS

1.    configure terminal

2.    port-channel load-balance extended [ dst-ip | dst-mac dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ]

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

port-channel load-balance extended [ dst-ip | dst-mac dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ]

Example:

Controller(config)# port-channel load-balance extended dst-ip dst-mac src-ip

Configures an EtherChannel extended load-balancing method.

The default is src-mac.

Select one of these load-distribution methods:

- dst-ip—Specifies destination-host IP address.

- dst-mac—Specifies the destination-host MAC address of the incoming packet.

- dst-port—Specifies the destination TCP/UDP port.

- ipv6-label—Specifies the IPv6 flow label.

- l3-proto—Specifies the Layer 3 protocol.

- src-ip—Specifies the source host IP address.

- src-mac—Specifies the source MAC address of the incoming packet.

- src-port—Specifies the source TCP/UDP port.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Configuring the PAgP Learn Method and Priority (CLI)

This task is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    pagp learn-method physical-port

4.    pagp port-priority priority

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies the port for transmission, and enters interface configuration mode.

Step 3

pagp learn-method physical-port

Example:

Controller(config-if)# pagp learn-method physical port

Selects the PAgP learning method.

By default, aggregation-port learning is selected, which means the controller sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives.

Selects physical-port to connect with another controller that is a physical learner. Make sure to configure the port-channel load-balance global configuration command to src-mac.

The learning method must be configured the same at both ends of the link.

Step 4

pagp port-priority priority

Example:

Controller(config-if)# pagp port-priority 200

Assigns a priority so that the selected port is chosen for packet transmission.

For priority, the range is 0 to 255. The default is 128. The higher the priority, the more likely that the port will be used for PAgP transmission.

Step 5

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Configuring LACP Hot-Standby Ports

When LACP is enabled, the software, by default, tries to configure the maximum number of LACP-compatible ports in a channel, up to a maximum of 16 ports. Only eight LACP links can be active at one time; the remaining eight links are placed in hot-standby mode. If one of the active links becomes inactive, a link that is in the hot-standby mode becomes active in its place.

You can override the default behavior by specifying the maximum number of active ports in a channel, in which case, the remaining ports become hot-standby ports. For example, if you specify a maximum of five ports in a channel, up to 11 ports become hot-standby ports.

If you configure more than eight links for an EtherChannel group, the software automatically decides which of the hot-standby ports to make active based on the LACP priority. To every link between systems that operate LACP, the software assigns a unique priority made up of these elements (in priority order):

- LACP system priority

- System ID (the controller MAC address)

- LACP port priority

- Port number

In priority comparisons, numerically lower values have higher priority. The priority decides which ports should be put in standby mode when there is a hardware limitation that prevents all compatible ports from aggregating.

Determining which ports are active and which are hot standby is a two-step procedure. First the system with a numerically lower system priority and system ID is placed in charge of the decision. Next, that system decides which ports are active and which are hot standby, based on its values for port priority and port number. The port priority and port number values for the other system are not used.

You can change the default values of the LACP system priority and the LACP port priority to affect how the software selects active and standby links.

- Configuring the LACP Max Bundle Feature (CLI)

- Configuring the Port Channel Min-Links Feature (CLI)

- Configuring the LACP System Priority (CLI)

- Configuring the LACP Port Priority (CLI)

Configuring the LACP Max Bundle Feature (CLI)

When you specify the maximum number of bundled LACP ports allowed in a port channel, the remaining ports in the port channel are designated as hot-standby ports.

Beginning in privileged EXEC mode, follow these steps to configure the maximum number of LACP ports in a port channel. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface port-channel channel-number

3.    lacp max-bundle max-bundle-number

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface port-channel channel-number

Example:

Controller(config)# interface port-channel 2

Enters interface configuration mode for a port channel.

The range is 1 to 128.

Step 3

lacp max-bundle max-bundle-number

Example:

Controller(config-if)# lacp max-bundle 3

Specifies the maximum number of LACP ports in the port-channel bundle.

The range is 1 to 8.

Step 4

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Configuring the Port Channel Min-Links Feature (CLI)

You can specify the minimum number of active ports that must be in the link-up state and bundled in an EtherChannel for the port channel interface to transition to the link-up state.

Beginning in privileged EXEC mode, follow these steps to configure the minimum number of links that are required for a port channel. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface port-channel channel-number

3.    port-channel min-links min-links-number

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface port-channel channel-number

Example:

Controller(config)# interface port-channel 2

Enters interface configuration mode for a port-channel.

For channel-number, the range is 1 to 128.

Step 3

port-channel min-links min-links-number

Example:

Controller(config-if)# port-channel min-links 3

Specifies the minimum number of member ports that must be in the link-up state and bundled in the EtherChannel for the port channel interface to transition to the link-up state.

For min-links-number , the range is 2 to 8.

Step 4

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Configuring the LACP System Priority (CLI)

You can configure the system priority for all the EtherChannels that are enabled for LACP by using the lacp system-priority global configuration command. You cannot configure a system priority for each LACP-configured channel. By changing this value from the default, you can affect how the software selects active and standby links.

You can use the show etherchannel summary privileged EXEC command to see which ports are in the hot-standby mode (denoted with an H port-state flag).

Beginning in privileged EXEC mode, follow these steps to configure the LACP system priority. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    lacp system-priority priority

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

lacp system-priority priority

Example:

Controller(config)# lacp system-priority 32000

Configures the LACP system priority.

The range is 1 to 65535. The default is 32768.

The lower the value, the higher the system priority.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Configuring the LACP Port Priority (CLI)

By default, all ports use the same port priority. If the local system has a lower value for the system priority and the system ID than the remote system, you can affect which of the hot-standby links become active first by changing the port priority of LACP EtherChannel ports to a lower value than the default. The hot-standby ports that have lower port numbers become active in the channel first. You can use the show etherchannel summary privileged EXEC command to see which ports are in the hot-standby mode (denoted with an H port-state flag).

Note

If LACP is not able to aggregate all the ports that are compatible (for example, the remote system might have more restrictive hardware limitations), all the ports that cannot be actively included in the EtherChannel are put in the hot-standby state and are used only if one of the channeled ports fails.

Beginning in privileged EXEC mode, follow these steps to configure the LACP port priority. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    lacp port-priority priority

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies the port to be configured, and enters interface configuration mode.

Step 3

lacp port-priority priority

Example:

Controller(config-if)# lacp port-priority 32000

Configures the LACP port priority.

The range is 1 to 65535. The default is 32768. The lower the value, the more likely that the port will be used for LACP transmission.

Step 4

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Monitoring EtherChannel, PAgP, and LACP Status

You can display EtherChannel, PAgP, and LACP status using the commands listed in this table.

Commands for Monitoring EtherChannel, PAgP, and LACP Status

Command

Description

clear lacp { channel-group-number counters | counters }

Clears LACP channel-group information and traffic counters.

clear pagp { channel-group-number counters | counters }

Clears PAgP channel-group information and traffic counters.

show etherchannel [ channel-group-number { detail | port | port-channel | protocol | summary }] [ detail | load-balance | port | port-channel | protocol | summary ]

Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.

show pagp [ channel-group-number ] { counters | internal | neighbor }

Displays PAgP information such as traffic information, the internal PAgP configuration, and neighbor information.

show pagp [ channel-group-number ] dual-active

Displays the dual-active detection status.

show lacp [ channel-group-number ] { counters | internal  | neighbor | sys-id}

Displays LACP information such as traffic information, the internal LACP configuration, and neighbor information.

show running-config

Verifies your configuration entries.

show etherchannel load-balance

Displays the load balance or frame distribution scheme among ports in the port channel.

Configuration Examples for Configuring EtherChannels

- Configuring Layer 2 EtherChannels: Examples

- Configuring Layer 3 EtherChannels: Examples

- Configuring LACP Hot-Standby Ports: Example

Configuring Layer 2 EtherChannels: Examples

This example shows how to configure an EtherChannel on a single controller in the stack. It assigns two ports as static-access ports in VLAN 10 to channel 5 with the PAgP mode desirable:

Controller# configure terminal
Controller(config)# interface range gigabitethernet2/0/1 -2
Controller(config-if-range)# switchport mode access
Controller(config-if-range)# switchport access vlan 10
Controller(config-if-range)# channel-group 5 mode desirable non-silent
Controller(config-if-range)# end

This example shows how to configure an EtherChannel on a single controller in the stack. It assigns two ports as static-access ports in VLAN 10 to channel 5 with the LACP mode active:

Controller# configure terminal
Controller(config)# interface range gigabitethernet2/0/1 -2
Controller(config-if-range)# switchport mode access
Controller(config-if-range)# switchport access vlan 10
Controller(config-if-range)# channel-group 5 mode active
Controller(config-if-range)# end

This example shows how to configure a cross-stack EtherChannel. It uses LACP passive mode and assigns two ports on stack member 1 and one port on stack member 2 as static-access ports in VLAN 10 to channel 5:

Controller# configure terminal
Controller(config)# interface range gigabitethernet2/0/4 -5
Controller(config-if-range)# switchport mode access
Controller(config-if-range)# switchport access vlan 10
Controller(config-if-range)# channel-group 5 mode passive
Controller(config-if-range)# exit
Controller(config)# interface gigabitethernet3/0/3
Controller(config-if)# switchport mode access
Controller(config-if)# switchport access vlan 10
Controller(config-if)# channel-group 5 mode passive
Controller(config-if)# exit

Configuring Layer 3 EtherChannels: Examples

This example shows how to configure a Layer 3 EtherChannel. It assigns two ports to channel 5 with the LACP mode active:

Controller# configure terminal
Controller(config)# interface range gigabitethernet2/0/1 -2
Controller(config-if-range)# no ip address
Controller(config-if-range)# no switchport
Controller(config-if-range)# channel-group 5 mode active
Controller(config-if-range)# end

This example shows how to configure a cross-stack Layer 3 EtherChannel. It assigns two ports on stack member 2 and one port on stack member 3 to channel 7 using LACP active mode:

Controller# configure terminal
Controller(config)# interface range gigabitethernet2/0/4 -5
Controller(config-if-range)# no ip address
Controller(config-if-range)# no switchport
Controller(config-if-range)# channel-group 7 mode active
Controller(config-if-range)# exit
Controller(config)# interface gigabitethernet3/0/3
Controller(config-if)# no ip address
Controller(config-if)# no switchport
Controller(config-if)# channel-group 7 mode active
Controller(config-if)# exit

Configuring LACP Hot-Standby Ports: Example

This example shows how to configure an Etherchannel (port channel 2) that will be active when there are at least three active ports, will comprise up to seven active ports and the remaining ports (up to nine) as hot-standby ports :

Controller# configure terminal
Controller(config)# interface port-channel 2
Controller(config-if)# port-channel min-links 3
Controller(config-if)# lacp max-bundle 7

Additional References for EtherChannels

Related Documents

Related Topic

Document Title

Layer 2 command reference

Layer 2 Command Reference (Cisco WLC 5700 Series)

Error Message Decoder

Description

Link

To help you research and resolve system error messages in this release, use the Error Message Decoder tool.

Click Here

Standards and RFCs

Standard/RFC

Title

None

—

MIBs

MIB

MIBs Link

All supported MIBs for this release.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

Click Here

Feature Information for EtherChannels

Release

Modification

Cisco IOS XE 3.2SE

This feature was introduced.

Cisco IOS XE 3.3SE

Support for the LACP max-bundle feature and the port channel min-links features was added.

Chapter 3. Configuring Flex Links and the MAC Address-Table Move Update Feature

- Finding Feature Information

- Restrictions for Configuring Flex Links and MAC Address-Table Move Update

- Information About Flex Links and MAC Address-Table Move Update

- How to Configure Flex Links and the MAC Address-Table Move Update Feature

- Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

- Configuration Examples for Flex Links

- Additional References for Flex Links and MAC Address-Table Move Update

- Feature Information for Flex Links and MAC Address-Table Move Update

Finding Feature Information

IEEE 802.1x port-based authentication prevents unauthorized devices (clients) from gaining access to the network. Unless otherwise noted, the term switch refers to a standalone switch and to a switch stack.

Note

Stacking is supported only on Catalyst 2960-S switches running the LAN base image.

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

- Flex Links are supported only on Layer 2 ports and port channels.

- You can configure up to 16 backup links.

- You can configure only one Flex Links backup link for any active link, and it must be a different interface from the active interface.

- An interface can belong to only one Flex Links pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Links pair.

- Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two port channels (EtherChannel logical interfaces) as Flex Links, and you can configure a port channel and a physical interface as Flex Links, with either the port channel or the physical interface as the active link.

- A backup link does not have to be the same type (Gigabit Ethernet or port channel) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link begins to forward traffic.

- STP is disabled on Flex Links ports. A Flex Links port does not participate in STP, even if the VLANs present on the port are configured for STP. When STP is not enabled, be sure that there are no loops in the configured topology.

Information About Flex Links and MAC Address-Table Move Update

- Flex Links

- VLAN Flex Links Load Balancing and Support

- Multicast Fast Convergence with Flex Links Failover

- MAC Address-Table Move Update

- Flex Links VLAN Load Balancing Configuration Guidelines

- MAC Address-Table Move Update Configuration Guidelines

- Default Flex Links and MAC Address-Table Move Update Configuration

Flex Links

Flex Links are a pair of a Layer 2 interfaces (controller ports or port channels) where one interface is configured to act as a backup to the other. The feature provides an alternative solution to the Spanning Tree Protocol (STP). Users can disable STP and still retain basic link redundancy. Flex Links are typically configured in service provider or enterprise networks where customers do not want to run STP on the controller. If the controller is running STP, Flex Links are not necessary because STP already provides link-level redundancy or backup.

You configure Flex Links on one Layer 2 interface (the active link) by assigning another Layer 2 interface as the Flex Links or backup link. On controllers, the Flex Links can be on the same controller or on another controller in the stack. When one of the links is up and forwarding traffic, the other link is in standby mode, ready to begin forwarding traffic if the other link shuts down. At any given time, only one of the interfaces is in the linkup state and forwarding traffic. If the primary link shuts down, the standby link starts forwarding traffic. When the active link comes back up, it goes into standby mode and does not forward traffic. STP is disabled on Flex Links interfaces.

- Flex Links Configuration

Flex Links Configuration

In the following figure, ports 1 and 2 on controller A are connected to uplink switches B and C. Because they are configured as Flex Links, only one of the interfaces is forwarding traffic; the other is in standby mode. If port 1 is the active link, it begins forwarding traffic between port 1 and switch B; the link between port 2 (the backup link) and switch C is not forwarding traffic. If port 1 goes down, port 2 comes up and starts forwarding traffic to switch C. When port 1 comes back up, it goes into standby mode and does not forward traffic; port 2 continues forwarding traffic.

You can also configure a preemption function, specifying the preferred port for forwarding traffic. For example, you can configure the Flex Links pair with preemption mode. In the scenario shown, when port 1 comes back up and has more bandwidth than port 2, port 1 begins forwarding traffic after 60 seconds. Port 2 becomes the standby port. You do this by entering the switchport backup interface preemption mode bandwidth and switchport backup interface preemption delay interface configuration commands.

Flex Links Configuration Example

If a primary (forwarding) link goes down, a trap notifies the network management stations. If the standby link goes down, a trap notifies the users.

Flex Links are supported only on Layer 2 ports and port channels, not on VLANs or on Layer 3 ports.

VLAN Flex Links Load Balancing and Support

VLAN Flex Links load balancing allows users to configure a Flex Links pair so that both ports simultaneously forward the traffic for some mutually exclusive VLANs. For example, if Flex Links ports are configured for 1 to 100 VLANs, the traffic of the first 50 VLANs can be forwarded on one port and the rest on the other port. If one of the ports fail, the other active port forwards all the traffic. When the failed port comes back up, it resumes forwarding traffic in the preferred VLANs. In addition to providing the redundancy, this Flex Links pair can be used for load balancing. Flex Links VLAN load balancing does not impose any restrictions on uplink controllers.

VLAN Flex Links Load-Balancing Configuration Example

Multicast Fast Convergence with Flex Links Failover

Multicast fast convergence reduces the multicast traffic convergence time after a Flex Links failure. Multicast fast convergence is implemented by a combination of learning the backup link as an mrouter port, generating IGMP reports, and leaking IGMP reports.

- Learning the Other Flex Links Port as the mrouter Port

- Generating IGMP Reports

- Leaking IGMP Reports

Learning the Other Flex Links Port as the mrouter Port

In a typical multicast network, there is a querier for each VLAN. A controller deployed at the edge of a network has one of its Flex Links ports receiving queries. Flex Links ports are also always forwarding at any given time.

A port that receives queries is added as an mrouter port on the controller. An mrouter port is part of all the multicast groups learned by the controller. After a changeover, queries are received by the other Flex Links port. The other Flex Links port is then learned as the mrouter port. After changeover, multicast traffic then flows through the other Flex Links port. To achieve faster convergence of traffic, both Flex Links ports are learned as mrouter ports whenever either Flex Links port is learned as the mrouter port. Both Flex Links ports are always part of multicast groups.

Although both Flex Links ports are part of the groups in normal operation mode, all traffic on the backup port is blocked. The normal multicast data flow is not affected by the addition of the backup port as an mrouter port. When the changeover happens, the backup port is unblocked, allowing the traffic to flow. In this case, the upstream multicast data flows as soon as the backup port is unblocked.

Generating IGMP Reports

When the backup link comes up after the changeover, the upstream new distribution controller does not start forwarding multicast data, because the port on the upstream router, which is connected to the blocked Flex Links port, is not part of any multicast group. The reports for the multicast groups were not forwarded by the downstream controller because the backup link is blocked. The data does not flow on this port, until it learns the multicast groups, which occurs only after it receives reports.

The reports are sent by hosts when a general query is received, and a general query is sent within 60 seconds in normal scenarios. When the backup link starts forwarding, to achieve faster convergence of multicast data, the downstream controller immediately sends proxy reports for all the learned groups on this port without waiting for a general query.

Leaking IGMP Reports

To achieve multicast traffic convergence with minimal loss, a redundant data path must be set up before the Flex Links active link goes down. This can be achieved by leaking only IGMP report packets on the Flex Links backup link. These leaked IGMP report messages are processed by upstream distribution routers, so multicast data traffic gets forwarded to the backup interface. Because all incoming traffic on the backup interface is dropped at the ingress of the access controller, no duplicate multicast traffic is received by the host. When the Flex Links active link fails, the access controller starts accepting traffic from the backup link immediately. The only disadvantage of this scheme is that it consumes bandwidth on the link between the distribution controllers and on the backup link between the distribution and access controllers. This feature is disabled by default and can be configured by using the switchport backup interface interface-id multicast fast-convergence command.

When this feature has been enabled at changeover, the controller does not generate the proxy reports on the backup port, which became the forwarding port.

MAC Address-Table Move Update

The MAC address-table move update feature allows the controller to provide rapid bidirectional convergence when a primary (forwarding) link goes down and the standby link begins forwarding traffic.

MAC Address-Table Move Update Example. In the following figure, the controller and switches B and C form the Flexlink through a Flex Links pair. Port 3 is forwarding traffic, and port 4 is in the backup state. Switch A is an access switch, and ports 1 and 2 on switch A are connected to uplink switches B and C. The MAC addresses of the wireless clients have been learnt on port 1 of the switch A.

In the above figure, three wireless clients connect to an access point and communicate to the controller. The PC connected to switch A communicates with the wireless clients through the data path from port 3 to port 1. If the MAC address-table move update feature is not configured on the controller and port 3 goes down, port 4 starts forwarding traffic. However, for a short time the wireless clients will not be able to pass any traffic to the PC as port 3 is down.

If the MAC address-table move update feature is configured and enabled on the controller, and port 3 goes down, the controller sends a MAC address-table move update packet (MMU) from port 4. This MMU packet carries all the MAC addresses of the wireless clients. Switch C gets this packet on port 4 and immediately learns the MAC addresses of the wireless clients, which reduces the reconvergence time. The PC transmits data to the wireless clients using the path from port 2 to port 4. Switch C also bridges the same MMU packet in the VLAN so that all the switches in the network will update the MAC address table to ensure that the next packet to any wireless client towards controller comes on the right path. The controller learns only the MAC addresses of the wireless clients.

Flex Links VLAN Load Balancing Configuration Guidelines

- For Flex Links VLAN load balancing, you must choose the preferred VLANs on the backup interface.

- You cannot configure a preemption mechanism and VLAN load balancing for the same Flex Links pair.

MAC Address-Table Move Update Configuration Guidelines

- You can enable and configure this feature on the access controller to send the MAC address-table move updates.

- You can enable and configure this feature on the uplink controllers to get the MAC address-table move updates.

Default Flex Links and MAC Address-Table Move Update Configuration

- Flex Links is not configured, and there are no backup interfaces defined.

- The preemption mode is off.

- The preemption delay is 35 seconds.

- The MAC address-table move update feature is not configured on the controller.

How to Configure Flex Links and the MAC Address-Table Move Update Feature

- Configuring Flex Links (CLI)

- Configuring VLAN Load Balancing on Flex Links (CLI)

- Configuring MAC Address-Table Move Update (CLI)

Configuring Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface
gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

- Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    switchport backup interface interface-id preemption mode [forced | bandwidth | off]

5.    switchport backup interface interface-id preemption delay delay-time

6.    end

7.    show interface [interface-id] switchport backup

8.    copy running-config startup config

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

switchport backup interface interface-id preemption mode [forced | bandwidth | off]

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption mode forced

Configures a preemption mechanism and delay for a Flex Links interface pair. You can configure the preemption as:

- forced—(Optional) The active interface always preempts the backup.

- bandwidth—(Optional) The interface with the higher bandwidth always acts as the active interface.

- off—(Optional) No preemption occurs from active to backup.

Step 5

switchport backup interface interface-id preemption delay delay-time

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption delay 50

Configures the time delay until a port preempts another port.

Note:
Setting a delay time only works with forced and bandwidth modes.

Step 6

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

Step 7

show interface [interface-id] switchport backup

Example:

Controller# show interface gigabitethernet1/0/2 switchport backup

Verifies the configuration.

Step 8

copy running-config startup config

Example:

Controller# copy running-config startup config

(Optional) Saves your entries in the controller startup configuration file.

Configuring VLAN Load Balancing on Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id prefer vlan vlan-range

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller (config)# interface gigabitethernet2/0/6

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id prefer vlan vlan-range

Example:

Controller (config-if)# switchport backup interface
gigabitethernet2/0/8 prefer vlan 2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface and specifies the VLANs carried on the interface. The VLAN ID range is 1 to 4094.

Step 4

end

Example:

Controller (config-if)# end

Returns to privileged EXEC mode.

Configuring MAC Address-Table Move Update (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

4.    end

5.    mac address-table move update transmit

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller#interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

Example:

Controller(config-if)# switchport backup interface
gigabitethernet0/2 mmu primary vlan 2

Configures a physical Layer 2 interface (or port channel), as part of a Flex Links pair with the interface. The MAC address-table move update VLAN is the lowest VLAN ID on the interface.

Configure a physical Layer 2 interface (or port channel) and specifies the VLAN ID on the interface, which is used for sending the MAC address-table move update.

When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(config-if)# end

Returns to global configuration mode.

Step 5

mac address-table move update transmit

Example:

Controller(config)#
mac address-table move update
transmit

Enables the access controller to send MAC address-table move updates to other controllers in the network if the primary link goes down and the controller starts forwarding traffic through the standby link.

Step 6

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

- Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

SUMMARY STEPS

1.    configure terminal

2.    mac address-table move update receive

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

mac address-table move update receive

Example:

Controller (config)# mac address-table move update receive

Enables the controller to obtain and processes the MAC address-table move updates.

Step 3

end

Example:

Controller (config)# end

Returns to privileged EXEC mode.

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Configuration Examples for Flex Links

- Configuring Flex Links: Examples

- Configuring VLAN Load Balancing on Flex Links: Examples

- Configuring the MAC Address-Table Move Update: Examples

- Configuring Multicast Fast Convergence with Flex Links Failover: Examples

Configuring Flex Links: Examples

This example shows how to verify the configuration after you configure an interface with a backup interface:

Controller# show interface switchport backup

Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/1 GigabitEthernet1/0/2 Active Up/Backup Standby

This example shows how to verify the configuration after you configure the preemption mode as forced for a backup interface pair:

Controller# show interface switchport backup detail

Switch Backup Interface Pairs:

Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/211 GigabitEthernet1/0/2 Active Up/Backup Standby
Interface Pair : Gi1/0/1, Gi1/0/2
Preemption Mode : forced
Preemption Delay : 50 seconds
Bandwidth : 100000 Kbit (Gi1/0/1), 100000 Kbit (Gi1/0/2)
Mac Address Move Update Vlan : auto

Configuring VLAN Load Balancing on Flex Links: Examples

In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the controller:

Controller(config)# interface gigabitethernet 2/0/6
Controller(config-if)# switchport backup interface gigabitethernet 2/0/8 prefer vlan 60,100-120

When both interfaces are up, Gi2/0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi2/0/6 forwards traffic for VLANs 1 to 50.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface goes down (LINK_DOWN), VLANs preferred on this interface are moved to the peer interface of the Flex Links pair. In this example, if interface Gi2/0/6 goes down, Gi2/0/8 carries all VLANs of the Flex Links pair.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Down/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface comes up, VLANs preferred on this interface are blocked on the peer interface and moved to the forwarding state on the interface that has just come up. In this example, if interface Gi2/0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi2/0/8 and forwarded on Gi2/0/6.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

Controller# show interfaces switchport backup detail

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
FastEthernet1/0/3       FastEthernet1/0/4       Active Down/Backup Up

Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Preemption Mode  : off
Bandwidth : 10000 Kbit (Fa1/0/3), 100000 Kbit (Fa1/0/4)
Mac Address Move Update Vlan : auto

Configuring the MAC Address-Table Move Update: Examples

This example shows how to verify the configuration after you configure an access controller to send MAC address-table move updates:

Controller# show mac address-table move update

Switch-ID : 010b.4630.1780
Dst mac-address : 0180.c200.0010
Vlans/Macs supported : 1023/8320
Default/Current settings: Rcv Off/On, Xmt Off/On
Max packets per min : Rcv 40, Xmt 60
Rcv packet count : 5
Rcv conforming packet count : 5
Rcv invalid packet count : 0
Rcv packet count this min : 0
Rcv threshold exceed count : 0
Rcv last sequence# this min : 0
Rcv last interface : Po2
Rcv last src-mac-address : 000b.462d.c502
Rcv last switch-ID : 0403.fd6a.8700
Xmt packet count : 0
Xmt packet count this min : 0
Xmt threshold exceed count : 0
Xmt pak buf unavail cnt : 0
Xmt last interface : None

Configuring Multicast Fast Convergence with Flex Links Failover: Examples

These are configuration examples for learning the other Flex Links port as the mrouter port when Flex Links is configured on GigabitEthernet1/0/11 and GigabitEthernet1/0/12, and output for the show interfaces switchport backup command:

Controller# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Controller(config)# interface GigabitEthernet1/0/11
Controller(config-if)# switchport trunk encapsulation dot1q
Controller(config-if)# switchport mode trunk
Controller(config-if)# switchport backup interface GigabitEthernet1/0/12
Controller(config-if)# exit
Controller(config)# interface GigabitEthernet1/0/12
Controller(config-if)# switchport trunk encapsulation dot1q
Controller(config-if)# switchport mode trunk
Controller(config-if)# end
Controller# show interfaces switchport backup detail
Switch Backup Interface Pairs:
Active Interface Backup Interface State
GigabitEthernet1/0/11 GigabitEthernet1/0/12 Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : Off
Bandwidth : 100000 Kbit (Gi1/0/11), 100000 Kbit (Gi1/0/12)
Mac Address Move Update Vlan : auto

This output shows a querier for VLANs 1 and 401, with their queries reaching the controller through GigabitEthernet1/0/11:

Controller# show ip igmp snooping querier

Vlan         IP Address                 IGMP Version                     Port
-------------------------------------------------------------
1           1.1.1.1                   v2                     Gi1/0/11
401         41.41.41.1                 v2                     Gi1/0/11

This example is output for the show ip igmp snooping mrouter command for VLANs 1 and 401:

Controller# show ip igmp snooping mrouter

Vlan         ports
----         -----
1          Gi1/0/11(dynamic), Gi1/0/12(dynamic)
401         Gi1/0/11(dynamic), Gi1/0/12(dynamic)

Similarly, both Flex Links ports are part of learned groups. In this example, GigabitEthernet2/0/11 is a receiver/host in VLAN 1, which is interested in two multicast groups:

Controller# show ip igmp snooping groups

Vlan         Group             Type         Version             Port List
-----------------------------------------------------------------------
1         228.1.5.1             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11
1         228.1.5.2             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11

When a host responds to the general query, the controller forwards this report on all the mrouter ports. In this example, when a host sends a report for the group 228.1.5.1, it is forwarded only on GigabitEthernet1/0/11, because the backup port GigabitEthernet1/0/12 is blocked. When the active link, GigabitEthernet1/0/11, goes down, the backup port, GigabitEthernet1/0/12, begins forwarding.

As soon as this port starts forwarding, the controller sends proxy reports for the groups 228.1.5.1 and 228.1.5.2 on behalf of the host. The upstream router learns the groups and starts forwarding multicast data. This is the default behavior of Flex Links. This behavior changes when the user configures fast convergence using the switchport backup interface gigabitEthernet 1/0/12 multicast fast-convergence command. This example shows turning on this feature:

Controller# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Controller(config)# interface gigabitEthernet 1/0/11
Controller(config-if)# switchport backup interface gigabitEthernet 1/0/12 multicast fast-convergence
Controller(config-if)# exit
Controller# show interfaces switchport backup detail

Switch Backup Interface Pairs:
Active                         Interface                         Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/11     GigabitEthernet1/0/12     Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : On
Bandwidth : 100000 Kbit (Gi1/0/11), 100000 Kbit (Gi1/0/12)
Mac Address Move Update Vlan : auto

This output shows a querier for VLAN 1 and 401 with their queries reaching the controller through GigabitEthernet1/0/11:

Controller# show ip igmp snooping querier

Vlan             IP Address                 IGMP Version                 Port
-------------------------------------------------------------
1              1.1.1.1                   v2                 Gi1/0/11
401             41.41.41.1                 v2                 Gi1/0/11

This is output for the show ip igmp snooping mrouter command for VLAN 1 and 401:

Controller# show ip igmp snooping mrouter

Vlan             ports
----             -----
1             Gi1/0/11(dynamic), Gi1/0/12(dynamic)
401             Gi1/0/11(dynamic), Gi1/0/12(dynamic)

Similarly, both the Flex Links ports are a part of the learned groups. In this example, GigabitEthernet2/0/11 is a receiver/host in VLAN 1, which is interested in two multicast groups:

Controller# show ip igmp snooping groups

Vlan         Group             Type         Version             Port List
-----------------------------------------------------------------------
1         228.1.5.1             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11
1         228.1.5.2             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11

Whenever a host responds to the general query, the controller forwards this report on all the mrouter ports. When you turn on this feature through the command-line port, and when a report is forwarded by the controller on GigabitEthernet1/0/11, it is also leaked to the backup port GigabitEthernet1/0/12. The upstream router learns the groups and starts forwarding multicast data, which is dropped at the ingress because GigabitEthernet1/0/12 is blocked. When the active link, GigabitEthernet1/0/11, goes down, the backup port, GigabitEthernet1/0/12, begins forwarding. You do not need to send any proxy reports as the multicast data is already being forwarded by the upstream router. By leaking reports to the backup port, a redundant multicast path has been set up, and the time taken for the multicast traffic convergence is very minimal.

Additional References for Flex Links and MAC Address-Table Move Update

Related Documents

Related Topic

Document Title

Layer 2 command reference

Layer 2 Command Reference (Cisco WLC 5700 Series)

switchport backup interface command

Interface Command Reference (Cisco WLC 5700 Series)

Error Message Decoder

Description

Link

To help you research and resolve system error messages in this release, use the Error Message Decoder tool.

Click Here

Standards and RFCs

Standard/RFC

Title

None

—

MIBs

MIB

MIBs Link

All supported MIBs for this release.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

Click Here

Feature Information for Flex Links and MAC Address-Table Move Update

Release

Modification

Cisco IOS XE 3.2SE

This feature was introduced.

Cisco IOS XE 3.3SE

Support for multicast fast convergence with Flex Links failover was added.

Chapter 4. Configuring UniDirectional Link Detection

- Finding Feature Information

- Restrictions for Configuring UDLD

- Information About UDLD

- How to Configure UDLD

- Monitoring and Maintaining UDLD

- Additional References for UDLD

- Feature Information for UDLD

Finding Feature Information

IEEE 802.1x port-based authentication prevents unauthorized devices (clients) from gaining access to the network. Unless otherwise noted, the term switch refers to a standalone switch and to a switch stack.

Note

Stacking is supported only on Catalyst 2960-S switches running the LAN base image.

Restrictions for Configuring UDLD

The following are restrictions for configuring UniDirectional Link Detection (UDLD):

- A UDLD-capable port cannot detect a unidirectional link if it is connected to a UDLD-incapable port of another controller.

- When configuring the mode (normal or aggressive), make sure that the same mode is configured on both sides of the link.

Caution

Loop guard works only on point-to-point links. We recommend that each end of the link has a directly connected device that is running STP.

Information About UDLD

UniDirectional Link Detection (UDLD) is a Layer 2 protocol that enables devices connected through fiber-optic or twisted-pair Ethernet cables to monitor the physical configuration of the cables and detect when a unidirectional link exists. All connected devices must support UDLD for the protocol to successfully identify and disable unidirectional links. When UDLD detects a unidirectional link, it disables the affected port and alerts you. Unidirectional links can cause a variety of problems, including spanning-tree topology loops.

- Modes of Operation

- Methods to Detect Unidirectional Links

- Default UDLD Configuration

Modes of Operation

UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD can detect unidirectional links due to misconnected ports on fiber-optic connections. In aggressive mode, UDLD can also detect unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and to misconnected ports on fiber-optic links.

In normal and aggressive modes, UDLD works with the Layer 1 mechanisms to learn 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 ports. When you enable both autonegotiation and UDLD, the 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 sent by a local device is received by its neighbor but traffic from the neighbor is not received by the local device.

- Normal Mode

- Aggressive Mode

Normal Mode

In normal mode, UDLD detects a unidirectional link when fiber strands in a fiber-optic port are misconnected and the Layer 1 mechanisms do not detect this misconnection. If the ports are connected correctly but the traffic is one way, UDLD does not detect the unidirectional link because the Layer 1 mechanism, which is supposed to detect this condition, does not do so. In this case, the logical link is considered undetermined, and UDLD does not disable the port.

When UDLD is in normal mode, if one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up because the Layer 1 mechanisms detects a physical problem with the link. In this case, UDLD does not take any action and the logical link is considered undetermined.

Aggressive Mode

In aggressive mode, UDLD detects a unidirectional link by using the previous detection methods. UDLD in aggressive mode can also detect a unidirectional link on a point-to-point link on which no failure between the two devices is allowed. It can also detect a unidirectional link when one of these problems exists:

- On fiber-optic or twisted-pair links, one of the ports cannot send or receive traffic.

- On fiber-optic or twisted-pair links, one of the ports is down while the other is up.

- One of the fiber strands in the cable is disconnected.

In these cases, UDLD disables the affected port.

In a point-to-point link, UDLD hello packets can be considered as a heart beat whose presence guarantees the health of the link. Conversely, the loss of the heart beat means that the link must be shut down if it is not possible to reestablish a bidirectional link.

If both fiber strands in a cable are working normally from a Layer 1 perspective, UDLD in aggressive mode detects whether those fiber strands 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.

Methods to Detect Unidirectional Links

UDLD operates by using two methods:

- Neighbor database maintenance

- Event-driven detection and echoing

- Neighbor Database Maintenance

- Event-Driven Detection and Echoing

- UDLD Reset Options

Neighbor Database Maintenance

UDLD learns about other UDLD-capable neighbors by periodically sending a hello packet (also called an advertisement or probe) on every active port to keep each device informed about its neighbors.

When the controller receives a hello message, it caches the information until the age time (hold time or time-to-live) expires. If the controller receives a new hello message before an older cache entry ages, the controller replaces the older entry with the new one.

Whenever a port is disabled and UDLD is running, whenever UDLD is disabled on a port, or whenever the controller is reset, UDLD clears all existing cache entries for the ports affected by the configuration change. UDLD sends at least one message to inform the neighbors to flush the part of their caches affected by the status change. The message is intended to keep the caches synchronized.

Event-Driven Detection and Echoing

UDLD relies on echoing as its detection operation. Whenever a UDLD device learns about a new neighbor or receives a resynchronization request from an out-of-sync neighbor, it restarts the detection window on its side of the connection and sends echo messages in reply. Because this behavior is the same on all UDLD neighbors, the sender of the echoes expects to receive an echo in reply.

If the detection window ends and no valid reply message is received, the link might shut down, depending on the UDLD mode. When UDLD is in normal mode, the link might be considered undetermined and might not be shut down. When UDLD is in aggressive mode, the link is considered unidirectional, and the port is disabled.

UDLD Reset Options

If an interface becomes disabled by UDLD, you can use one of the following options to reset UDLD:

- The udld reset interface configuration command.

- The shutdown interface configuration command followed by the no shutdown interface configuration command restarts the disabled port.

- The no udld {aggressive | enable} global configuration command followed by the udld {aggressive | enable} global configuration command reenables the disabled ports.

- The no udld port interface configuration command followed by the udld port [aggressive] interface configuration command reenables the disabled fiber-optic port.

- The errdisable recovery cause udld global configuration command enables the timer to automatically recover from the UDLD error-disabled state, and the errdisable recovery interval interval global configuration command specifies the time to recover from the UDLD error-disabled state.

Default UDLD Configuration

Default UDLD Configuration

Feature

Default Setting

UDLD global enable state

Globally disabled

UDLD per-port enable state for fiber-optic media

Disabled on all Ethernet fiber-optic ports

UDLD per-port enable state for twisted-pair (copper) media

Disabled on all Ethernet 10/100 and 1000BASE-TX ports

UDLD aggressive mode

Disabled

How to Configure UDLD

- Enabling UDLD Globally (CLI)

- Enabling UDLD on an Interface (CLI)

Enabling UDLD Globally (CLI)

Follow these steps to enable UDLD in the aggressive or normal mode and to set the configurable message timer on all fiber-optic ports on the controller.

SUMMARY STEPS

1.    configure terminal

2.    udld {aggressive | enable | message time message-timer-interval}

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

udld {aggressive | enable | message time message-timer-interval}

Example:

Controller(config)# udld enable
message time 10

Specifies the UDLD mode of operation:

- aggressive—Enables UDLD in aggressive mode on all fiber-optic ports.

- enable—Enables UDLD in normal mode on all fiber-optic ports on the controller. UDLD is disabled by default. An individual interface configuration overrides the setting of the udld enable global configuration command.

- message time message-timer-interval—Configures the period of time between UDLD probe messages on ports that are in the advertisement phase and are detected to be bidirectional. The range is from 1 to 90 seconds; the default value is 15.
Note:
This command affects fiber-optic ports only. Use the udld interface configuration command to enable UDLD on other port types.

Use the no form of this command, to disable UDLD.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Enabling UDLD on an Interface (CLI)

Follow these steps either to enable UDLD in the aggressive or normal mode or to disable UDLD on a port.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    udld port [aggressive]

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface
gigabitethernet 1/0/1

Specifies the port to be enabled for UDLD, and enters interface configuration mode.

Step 3

udld port [aggressive]

Example:

Controller(config-if)# udld port aggressive

UDLD is disabled by default.

- udld port—Enables UDLD in normal mode on the specified port.

- udld port aggressive—(Optional) Enables UDLD in aggressive mode on the specified port.

Note:
Use the no udld port interface configuration command to disable UDLD on a specified fiber-optic port.

Step 4

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Monitoring and Maintaining UDLD

Command

Purpose

show udld [interface-id | neighbors]

Displays the UDLD status for the specified port or for all ports.

Additional References for UDLD

Related Documents

Related Topic

Document Title

Layer 2 command reference

Layer 2 Command Reference (Cisco WLC 5700 Series)

Error Message Decoder

Description

Link

To help you research and resolve system error messages in this release, use the Error Message Decoder tool.

Click Here

Standards and RFCs

Standard/RFC

Title

None

—

MIBs

MIB

MIBs Link

All supported MIBs for this release.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

Click Here

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

Click Here

Feature Information for UDLD

Release

Modification

Cisco IOS XE 3.2SE

This feature was introduced.

Preface

- Obtaining Documentation and Submitting a Service Request

- Document Conventions

- Related Documentation

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:

Click Here

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.

Document Conventions

This document uses the following conventions:

Convention

Description

^ or Ctrl

Both the ^ symbol and Ctrl represent the Control (Ctrl) key on a keyboard. For example, the key combination ^D or Ctrl-D means that you hold down the Control key while you press the D key. (Keys are indicated in capital letters but are not case sensitive.)

bold font

Commands and keywords and user-entered text appear in bold font.

Italic font

Document titles, new or emphasized terms, and arguments for which you supply values are in italic font.

Courier font

Terminal sessions and information the system displays appear in courier font.

Bold Courier font

Bold Courier font indicates text that the user must enter.

[x]

Elements in square brackets are optional.

...

An ellipsis (three consecutive nonbolded periods without spaces) after a syntax element indicates that the element can be repeated.

|

A vertical line, called a pipe, indicates a choice within a set of keywords or arguments.

[x | y]

Optional alternative keywords are grouped in brackets and separated by vertical bars.

{x | y}

Required alternative keywords are grouped in braces and separated by vertical bars.

[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.

string

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

< >

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.

Reader Alert Conventions

This document may use the following conventions for reader alerts:

Note

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

Tip

Means the following information will help you solve a problem.

Caution

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

Timesaver

Means the described action saves time. You can save time by performing the action described in the paragraph.

Warning

IMPORTANT SAFETY INSTRUCTIONS

This warning symbol means danger. You are in a situation that could cause bodily injury. Before you work on any equipment, be aware of the hazards involved with electrical circuitry and be familiar with standard practices for preventing accidents. Use the statement number provided at the end of each warning to locate its translation in the translated safety warnings that accompanied this device. Statement 1071

SAVE THESE INSTRUCTIONS

Related Documentation

Note

Before installing or upgrading the controller, refer to the controller release notes.

- documentation, located at:

- Cisco Validated Designs documents, located at: Click Here

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.

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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: Click Here . 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)

Configuring Layer 2 EtherChannels (CLI)

You configure Layer 2 EtherChannels by assigning ports to a channel group with the channel-group interface configuration command. This command automatically creates the port-channel logical interface.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport mode {access | trunk}

4.    switchport access vlan vlan-id

5.    channel-group channel-group-number mode {auto [non-silent] | desirable [non-silent ] | on } | { active | passive}

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters the global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet2/0/1

Specifies a physical port, and enters interface configuration mode.

Valid interfaces are physical ports.

For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group.

For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

Step 3

switchport mode {access | trunk}

Example:

Controller(config-if)# switchport mode access

Assigns all ports as static-access ports in the same VLAN, or configure them as trunks.

If you configure the port as a static-access port, assign it to only one VLAN. The range is 1 to 4094.

Step 4

switchport access vlan vlan-id

Example:

Controller(config-if)# switchport access vlan 22

(Optional) If you configure the port as a static-access port, assign it to only one VLAN. The range is 1 to 4094.

Step 5

channel-group channel-group-number mode {auto [non-silent] | desirable [non-silent ] | on } | { active | passive}

Example:

Controller(config-if)# channel-group 5 mode auto

Assigns the port to a channel group, and specifies the PAgP or the LACP mode.

For channel-group-number, the range is 1 to 128.

For mode, select one of these keywords:

- auto —Enables PAgP only if a PAgP device is detected. It places the port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation.This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- desirable —Unconditionally enables PAgP. It places the port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- on —Forces the port to channel without PAgP or LACP. In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode.

- non-silent —(Optional) If your controller is connected to a partner that is PAgP-capable, configures the controller port for nonsilent operation when the port is in the auto or desirable mode. If you do not specify non-silent, silent is assumed. The silent setting is for connections to file servers or packet analyzers. This setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

- active—Enables LACP only if a LACP device is detected. It places the port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

- passive —Enables LACP on the port and places it into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation.

Step 6

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related Concepts

EtherChannel Overview

EtherChannel Modes

EtherChannel on Controllers

EtherChannel Link Failover

LACP Modes

PAgP Modes

Silent Mode

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

EtherChannel Overview

EtherChannel provides fault-tolerant high-speed links between switches, routers, and servers. You can use the EtherChannel to increase the bandwidth between the wiring closets and the data center, and you can deploy it anywhere in the network where bottlenecks are likely to occur. EtherChannel provides automatic recovery for the loss of a link by redistributing the load across the remaining links. If a link fails, EtherChannel redirects traffic from the failed link to the remaining links in the channel without intervention.

An EtherChannel consists of individual Ethernet links bundled into a single logical link.

Typical EtherChannel Configuration

The EtherChannel provides full-duplex bandwidth up to 8 Gb/s (Gigabit EtherChannel) or 80 Gb/s (10-Gigabit EtherChannel) between your switch and another switch or host.

Each EtherChannel can consist of up to eight compatibly configured Ethernet ports.

The number of EtherChannels is limited to 128.

All ports in each EtherChannel must be configured as either Layer 2 or Layer 3 ports. The EtherChannel Layer 3 ports are made up of routed ports. Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface configuration command.

- EtherChannel Modes

- EtherChannel on Controllers

- EtherChannel Link Failover

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

EtherChannel Modes

You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), or On. Configure both ends of the EtherChannel in the same mode:

- When you configure one end of an EtherChannel in either PAgP or LACP mode, the system negotiates with the other end of the channel to determine which ports should become active. If the remote port cannot negotiate an EtherChannel, the local port is put into an independent state and continues to carry data traffic as would any other single link. The port configuration does not change, but the port does not participate in the EtherChannel.

- When you configure an EtherChannel in the on mode, no negotiations take place. The switch forces all compatible ports to become active in the EtherChannel. The other end of the channel (on the other switch) must also be configured in the on mode; otherwise, packet loss can occur.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

EtherChannel on Controllers

You can create an EtherChannel on a controller, on a single controller in the stack, or on multiple controllers in the stack (known as cross-stack EtherChannel).

Single Controller EtherChannel

This figure shows the recommended cross-stack EtherChannel configuration with three active links and three standby links.

Cross-Stack EtherChannel

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

EtherChannel Link Failover

If a link within an EtherChannel fails, traffic previously carried over that failed link moves to the remaining links within the EtherChannel. If traps are enabled on the switch, a trap is sent for a failure that identifies the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast packets on one link in an EtherChannel are blocked from returning on any other link of the EtherChannel.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

LACP Modes

LACP modes specify whether a port can send LACP packets or only receive LACP packets.

EtherChannel LACP Modes

Mode

Description

active

Places a port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

passive

Places a port into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation. This setting minimizes the transmission of LACP packets.

Both the active and passive LACP modes enable ports to negotiate with partner ports to an EtherChannel based on criteria such as port speed, and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different LACP modes as long as the modes are compatible. For example:

- A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.

- A port in the passive mode cannot form an EtherChannel with another port that is also in the passive mode because neither port starts LACP negotiation.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

PAgP Modes

PAgP modes specify whether a port can send PAgP packets, which start PAgP negotiations, or only respond to PAgP packets received.

EtherChannel PAgP Modes

Mode

Description

auto

Places a port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

desirable

Places a port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets.

Switch ports exchange PAgP packets only with partner ports configured in the auto or desirable modes. Ports configured in the on mode do not exchange PAgP packets.

Both the auto and desirable modes enable ports to negotiate with partner ports to form an EtherChannel based on criteria such as port speed. and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:

- A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

- A port in the auto mode can form an EtherChannel with another port in the desirable mode.

A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.

- Silent Mode

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

Silent Mode

If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.

Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Concepts

EtherChannel Overview

EtherChannel Modes

EtherChannel on Controllers

EtherChannel Link Failover

LACP Modes

PAgP Modes

Silent Mode

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Concepts

EtherChannel Overview

EtherChannel Modes

EtherChannel on Controllers

EtherChannel Link Failover

LACP Modes

PAgP Modes

Silent Mode

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Concepts

EtherChannel Overview

EtherChannel Modes

EtherChannel on Controllers

EtherChannel Link Failover

LACP Modes

PAgP Modes

Silent Mode

Related Tasks

Configuring Layer 2 EtherChannels (CLI)

Creating Port-Channel Logical Interfaces (CLI)

When configuring Layer 3 EtherChannels, you should first manually create the port-channel logical interface by using the interface port-channel global configuration command. Then put the logical interface into the channel group by using the channel-group interface configuration command.

Note

To move an IP address from a physical port to an EtherChannel, you must delete the IP address from the physical port before configuring it on the port-channel interface.

Beginning in privileged EXEC mode, follow these steps to create a port-channel interface for a Layer 3 EtherChannel. This procedure is required.

SUMMARY STEPS

1.    configure terminal

2.    interface port-channel port-channel-number

3.    no switchport

4.    ip address ip-address mask

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface port-channel port-channel-number

Example:

Controller(config)# interface port-channel 5

Specifies the port-channel logical interface, and enters interface configuration mode.

For port-channel-number, the range is 1 to 48.

Step 3

no switchport

Example:

Controller(config-if)# no switchport

Puts the interface into Layer 3 mode.

Step 4

ip address ip-address mask

Example:

Controller(config-if)# ip address ip address 172.10.20.10 255.255.255.0

Assigns an IP address and subnet mask to the EtherChannel.

Step 5

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

This example shows how to create the logical port channel 5 and assign 172.10.20.10 as its IP address:

Switch# configure terminal
Switch(config)# interface port-channel 5
Switch(config-if)# no switchport
Switch(config-if)# ip address 172.10.20.10 255.255.255.0
Switch(config-if)# end

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Channel Groups and Port-Channel Interfaces

An EtherChannel comprises a channel group and a port-channel interface. The channel group binds physical ports to the port-channel interface. Configuration changes applied to the port-channel interface apply to all the physical ports bound together in the channel group.

Relationship of Physical Ports, Channel Group and Port-Channel Interface.
The channel-group command binds the physical port and the port-channel interface together. Each EtherChannel has a port-channel logical interface numbered from 1 to 128. This port-channel interface number corresponds to the one specified with the channel-group interface configuration command.

- With Layer 2 ports, use the channel-group interface configuration command to dynamically create the port-channel interface. You also can use the interface port-channel port-channel-number global configuration command to manually create the port-channel interface, but then you must use the channel-group channel-group-number command to bind the logical interface to a physical port. The channel-group-number can be the same as the port-channel-number, or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.

- With Layer 3 ports, you should manually create the logical interface by using the interface port-channel global configuration command followed by the no switchport interface configuration command. You then manually assign an interface to the EtherChannel by using the channel-group interface configuration command.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

PAgP Modes

PAgP modes specify whether a port can send PAgP packets, which start PAgP negotiations, or only respond to PAgP packets received.

EtherChannel PAgP Modes

Mode

Description

auto

Places a port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

desirable

Places a port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets.

Switch ports exchange PAgP packets only with partner ports configured in the auto or desirable modes. Ports configured in the on mode do not exchange PAgP packets.

Both the auto and desirable modes enable ports to negotiate with partner ports to form an EtherChannel based on criteria such as port speed. and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:

- A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

- A port in the auto mode can form an EtherChannel with another port in the desirable mode.

A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.

- Silent Mode

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

Silent Mode

If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.

Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Creating Port-Channel Logical Interfaces (CLI)

Configuring the Physical Interfaces (CLI)

Beginning in privileged EXEC mode, follow these steps to assign an Ethernet port to a Layer 3 EtherChannel. This procedure is required.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    no ip address

4.    no switchport

5.    channel-group channel-group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive }

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies a physical port, and enters interface configuration mode.

Valid interfaces include physical ports.

For a PAgP EtherChannel, you can configure up to eight ports of the same type and speed for the same group.

For a LACP EtherChannel, you can configure up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

Step 3

no ip address

Example:

Controller(config-if)# no ip address

Ensures that there is no IP address assigned to the physical port.

Step 4

no switchport

Example:

Controller(config-if)# no switchport

Puts the port into Layer 3 mode.

Step 5

channel-group channel-group-number mode { auto [ non-silent ] | desirable [ non-silent ] | on } | { active | passive }

Example:

Controller(config-if)# channel-group 5 mode auto

Assigns the port to a channel group, and specifies the PAgP or the LACP mode.

For channel-group-number, the range is 1 to 48. This number must be that of a previously created port channel (logical port).

For mode, select one of these keywords:

- auto—Enables PAgP only if a PAgP device is detected. It places the port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- desirable—Unconditionally enables PAgP. It places the port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets. This keyword is not supported when EtherChannel members are from different controllers in the controller stack.

- on—Forces the port to channel without PAgP or LACP. In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode.

- non-silent—(Optional) If your controller is connected to a partner that is PAgP capable, configures the controller port for nonsilent operation when the port is in the auto or desirable mode. If you do not specify non-silent, silent is assumed. The silent setting is for connections to file servers or packet analyzers. This setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

- active—Enables LACP only if a LACP device is detected. It places the port into an active negotiating state in which the port starts negotiations with other ports by sending LACP packets.

- passive —Enables LACP on the port and places it into a passive negotiating state in which the port responds to LACP packets that it receives, but does not start LACP packet negotiation.

Step 6

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Channel Groups and Port-Channel Interfaces

An EtherChannel comprises a channel group and a port-channel interface. The channel group binds physical ports to the port-channel interface. Configuration changes applied to the port-channel interface apply to all the physical ports bound together in the channel group.

Relationship of Physical Ports, Channel Group and Port-Channel Interface.
The channel-group command binds the physical port and the port-channel interface together. Each EtherChannel has a port-channel logical interface numbered from 1 to 128. This port-channel interface number corresponds to the one specified with the channel-group interface configuration command.

- With Layer 2 ports, use the channel-group interface configuration command to dynamically create the port-channel interface. You also can use the interface port-channel port-channel-number global configuration command to manually create the port-channel interface, but then you must use the channel-group channel-group-number command to bind the logical interface to a physical port. The channel-group-number can be the same as the port-channel-number, or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.

- With Layer 3 ports, you should manually create the logical interface by using the interface port-channel global configuration command followed by the no switchport interface configuration command. You then manually assign an interface to the EtherChannel by using the channel-group interface configuration command.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring the Physical Interfaces (CLI)

PAgP Modes

PAgP modes specify whether a port can send PAgP packets, which start PAgP negotiations, or only respond to PAgP packets received.

EtherChannel PAgP Modes

Mode

Description

auto

Places a port into a passive negotiating state, in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. This setting minimizes the transmission of PAgP packets.

desirable

Places a port into an active negotiating state, in which the port starts negotiations with other ports by sending PAgP packets.

Switch ports exchange PAgP packets only with partner ports configured in the auto or desirable modes. Ports configured in the on mode do not exchange PAgP packets.

Both the auto and desirable modes enable ports to negotiate with partner ports to form an EtherChannel based on criteria such as port speed. and for Layer 2 EtherChannels, based on trunk state and VLAN numbers.

Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible. For example:

- A port in the desirable mode can form an EtherChannel with another port that is in the desirable or auto mode.

- A port in the auto mode can form an EtherChannel with another port in the desirable mode.

A port in the auto mode cannot form an EtherChannel with another port that is also in the auto mode because neither port starts PAgP negotiation.

- Silent Mode

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring the Physical Interfaces (CLI)

Silent Mode

If your switch is connected to a partner that is PAgP-capable, you can configure the switch port for nonsilent operation by using the non-silent keyword. If you do not specify non-silent with the auto or desirable mode, silent mode is assumed.

Use the silent mode when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port connected to a silent partner prevents that switch port from ever becoming operational. However, the silent setting allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring the Physical Interfaces (CLI)

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Configuring the Physical Interfaces (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Configuring the Physical Interfaces (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Concepts

Channel Groups and Port-Channel Interfaces

PAgP Modes

Silent Mode

Related Tasks

Configuring the Physical Interfaces (CLI)

Configuring EtherChannel Load-Balancing (CLI)

You can configure EtherChannel load-balancing to use one of several different forwarding methods.

This task is optional.

SUMMARY STEPS

1.    configure terminal

2.    port-channel load-balance { dst-ip | dst-mac | dst-mixed-ip-port | dst-port | extended [dst-ip | dst-mac | dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ] | src-dst-ip | src-dst-mac src-dst-mixed-ip-port src-dst-portsrc-ip | src-mac | src-mixed-ip-port | src-port}

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

port-channel load-balance { dst-ip | dst-mac | dst-mixed-ip-port | dst-port | extended [dst-ip | dst-mac | dst-port | ipv6-label | l3-proto | src-ip | src-mac | src-port ] | src-dst-ip | src-dst-mac src-dst-mixed-ip-port src-dst-portsrc-ip | src-mac | src-mixed-ip-port | src-port}

Example:

Controller(config)# port-channel load-balance src-mac

Configures an EtherChannel load-balancing method.

The default is src-mac.

Select one of these load-distribution methods:

- dst-ip—Specifies destination-host IP address.

- dst-mac—Specifies the destination-host MAC address of the incoming packet.

- dst-mixed-ip-port—Specifies the host IP address and TCP/UDP port.

- dst-port—Specifies the destination TCP/UDP port.

- extended—Specifies extended load balance methods--combinations of source and destination methods beyond those available with the standard command.

- ipv6-label—Specifies the IPv6 flow label.

- l3-proto—Specifies the Layer 3 protocol.

- src-dst-ip—Specifies the source and destination host IP address.

- src-dst-mac—Specifies the source and destination host MAC address.

- src-dst-mixed-ip-port—Specifies the source and destination host IP address and TCP/UDP port.

- src-dst-port—Specifies the source and destination TCP/UDP port.

- src-ip—Specifies the source host IP address.

- src-mac—Specifies the source MAC address of the incoming packet.

- src-mixed-ip-port—Specifies the source host IP address and TCP/UDP port.

- src-port—Specifies the source TCP/UDP port.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 3 EtherChannel Configuration Guidelines

Load-Balancing and Forwarding Methods

EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel. You can specify one of several different load-balancing modes, including load distribution based on MAC addresses, IP addresses, source addresses, destination addresses, or both source and destination addresses. The selected mode applies to all EtherChannels configured on the controller.

You configure the load-balancing and forwarding method by using the port-channel load-balance and the port-channel load-balance extendedglobal configuration commands.

- MAC Address Forwarding

- IP Address Forwarding

- Load-Balancing Advantages

Related Concepts

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 3 EtherChannel Configuration Guidelines

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

MAC Address Forwarding

With source-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide load-balancing, packets from different hosts use different ports in the channel, but packets from the same host use the same port in the channel.

With destination-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on the destination host’s MAC address of the incoming packet. Therefore, packets to the same destination are forwarded over the same port, and packets to a different destination are sent on a different port in the channel.

With source-and-destination MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed across the ports in the channel based on both the source and destination MAC addresses. This forwarding method, a combination source-MAC and destination-MAC address forwarding methods of load distribution, can be used if it is not clear whether source-MAC or destination-MAC address forwarding is better suited on a particular controller. With source-and-destination MAC-address forwarding, packets sent from host A to host B, host A to host C, and host C to host B could all use different ports in the channel.

Related Concepts

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 3 EtherChannel Configuration Guidelines

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

IP Address Forwarding

With source-IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on the source-IP address of the incoming packet. To provide load balancing, packets from different IP addresses use different ports in the channel, and packets from the same IP address use the same port in the channel.

With destination-IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on the destination-IP address of the incoming packet. To provide load balancing, packets from the same IP source address sent to different IP destination addresses could be sent on different ports in the channel. Packets sent from different source IP addresses to the same destination IP address are always sent on the same port in the channel.

With source-and-destination IP address-based forwarding, packets are distributed across the ports in the EtherChannel based on both the source and destination IP addresses of the incoming packet. This forwarding method, a combination of source-IP and destination-IP address-based forwarding, can be used if it is not clear whether source-IP or destination-IP address-based forwarding is better suited on a particular controller. In this method, packets sent from the IP address A to IP address B, from IP address A to IP address C, and from IP address C to IP address B could all use different ports in the channel.

Related Concepts

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 3 EtherChannel Configuration Guidelines

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

Load-Balancing Advantages

Different load-balancing methods have different advantages, and the choice of a particular load-balancing method should be based on the position of the controller in the network and the kind of traffic that needs to be load-distributed.

Load Distribution and Forwarding. In the figure below the controller does source MAC-based forwarding over the EtherChannel links and evenly distributes the traffic over multiple links of the EtherChannel.

Use the option that provides the greatest variety in your configuration. For example, if the traffic on a channel is going only to a single MAC address, using the destination-MAC address always chooses the same link in the channel. Using source addresses or IP addresses might result in better load-balancing.

Related Concepts

EtherChannel Configuration Guidelines

Layer 2 EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 3 EtherChannel Configuration Guidelines

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Concepts

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Concepts

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Concepts

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

Layer 3 EtherChannel Configuration Guidelines

- For Layer 3 EtherChannels, assign the Layer 3 address to the port-channel logical interface, not to the physical ports in the channel.

Related Concepts

Load-Balancing and Forwarding Methods

MAC Address Forwarding

IP Address Forwarding

Load-Balancing Advantages

Related Tasks

Configuring EtherChannel Load-Balancing (CLI)

Configuring the PAgP Learn Method and Priority (CLI)

This task is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    pagp learn-method physical-port

4.    pagp port-priority priority

5.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies the port for transmission, and enters interface configuration mode.

Step 3

pagp learn-method physical-port

Example:

Controller(config-if)# pagp learn-method physical port

Selects the PAgP learning method.

By default, aggregation-port learning is selected, which means the controller sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives.

Selects physical-port to connect with another controller that is a physical learner. Make sure to configure the port-channel load-balance global configuration command to src-mac.

The learning method must be configured the same at both ends of the link.

Step 4

pagp port-priority priority

Example:

Controller(config-if)# pagp port-priority 200

Assigns a priority so that the selected port is chosen for packet transmission.

For priority, the range is 0 to 255. The default is 128. The higher the priority, the more likely that the port will be used for PAgP transmission.

Step 5

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related Concepts

PAgP Learn Method and Priority

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related References

Monitoring EtherChannel, PAgP, and LACP Status

PAgP Learn Method and Priority

Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a physical learner if it learns addresses by physical ports and directs transmissions based on that knowledge. A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports. The learn method must be configured the same at both ends of the link.

When a device and its partner are both aggregate-port learners, they learn the address on the logical port-channel. The device sends packets to the source by using any of the ports in the EtherChannel. With aggregate-port learning, it is not important on which physical port the packet arrives.

PAgP cannot automatically detect when the partner device is a physical learner and when the local device is an aggregate-port learner. Therefore, you must manually set the learning method on the local device to learn addresses by physical ports. You also must set the load-distribution method to source-based distribution, so that any given source MAC address is always sent on the same physical port.

You also can configure a single port within the group for all transmissions and use other ports for hot-standby. The unused ports in the group can be swapped into operation in just a few seconds if the selected single port loses hardware-signal detection. You can configure which port is always selected for packet transmission by changing its priority with the pagp port-priority interface configuration command. The higher the priority, the more likely that the port will be selected.

Note

The controller supports address learning only on aggregate ports even though the physical-port keyword is provided in the CLI. The pagp learn-method command and the pagp port-priority command have no effect on the controller hardware, but they are required for PAgP interoperability with devices that only support address learning by physical ports, such as the Catalyst 1900 switch.

When the link partner of the controller is a physical learner, we recommend that you configure the controller as a physical-port learner by using the pagp learn-method physical-port interface configuration command. Set the load-distribution method based on the source MAC address by using the port-channel load-balance src-mac global configuration command. The controller then sends packets to the physcial learner using the same port in the EtherChannel from which it learned the source address. Only use the pagp learn-method command in this situation.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related Tasks

Configuring the PAgP Learn Method and Priority (CLI)

Related References

Monitoring EtherChannel, PAgP, and LACP Status

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Concepts

PAgP Learn Method and Priority

Related Tasks

Configuring the PAgP Learn Method and Priority (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Concepts

PAgP Learn Method and Priority

Related Tasks

Configuring the PAgP Learn Method and Priority (CLI)

Monitoring EtherChannel, PAgP, and LACP Status

You can display EtherChannel, PAgP, and LACP status using the commands listed in this table.

Commands for Monitoring EtherChannel, PAgP, and LACP Status

Command

Description

clear lacp { channel-group-number counters | counters }

Clears LACP channel-group information and traffic counters.

clear pagp { channel-group-number counters | counters }

Clears PAgP channel-group information and traffic counters.

show etherchannel [ channel-group-number { detail | port | port-channel | protocol | summary }] [ detail | load-balance | port | port-channel | protocol | summary ]

Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.

show pagp [ channel-group-number ] { counters | internal | neighbor }

Displays PAgP information such as traffic information, the internal PAgP configuration, and neighbor information.

show pagp [ channel-group-number ] dual-active

Displays the dual-active detection status.

show lacp [ channel-group-number ] { counters | internal  | neighbor | sys-id}

Displays LACP information such as traffic information, the internal LACP configuration, and neighbor information.

show running-config

Verifies your configuration entries.

show etherchannel load-balance

Displays the load balance or frame distribution scheme among ports in the port channel.

Related Concepts

PAgP Learn Method and Priority

Related Tasks

Configuring the PAgP Learn Method and Priority (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Concepts

PAgP Learn Method and Priority

Related Tasks

Configuring the PAgP Learn Method and Priority (CLI)

Configuring the LACP System Priority (CLI)

You can configure the system priority for all the EtherChannels that are enabled for LACP by using the lacp system-priority global configuration command. You cannot configure a system priority for each LACP-configured channel. By changing this value from the default, you can affect how the software selects active and standby links.

You can use the show etherchannel summary privileged EXEC command to see which ports are in the hot-standby mode (denoted with an H port-state flag).

Beginning in privileged EXEC mode, follow these steps to configure the LACP system priority. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    lacp system-priority priority

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

lacp system-priority priority

Example:

Controller(config)# lacp system-priority 32000

Configures the LACP system priority.

The range is 1 to 65535. The default is 32768.

The lower the value, the higher the system priority.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related References

Monitoring EtherChannel, PAgP, and LACP Status

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Tasks

Configuring the LACP System Priority (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Tasks

Configuring the LACP System Priority (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Tasks

Configuring the LACP System Priority (CLI)

Monitoring EtherChannel, PAgP, and LACP Status

You can display EtherChannel, PAgP, and LACP status using the commands listed in this table.

Commands for Monitoring EtherChannel, PAgP, and LACP Status

Command

Description

clear lacp { channel-group-number counters | counters }

Clears LACP channel-group information and traffic counters.

clear pagp { channel-group-number counters | counters }

Clears PAgP channel-group information and traffic counters.

show etherchannel [ channel-group-number { detail | port | port-channel | protocol | summary }] [ detail | load-balance | port | port-channel | protocol | summary ]

Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.

show pagp [ channel-group-number ] { counters | internal | neighbor }

Displays PAgP information such as traffic information, the internal PAgP configuration, and neighbor information.

show pagp [ channel-group-number ] dual-active

Displays the dual-active detection status.

show lacp [ channel-group-number ] { counters | internal  | neighbor | sys-id}

Displays LACP information such as traffic information, the internal LACP configuration, and neighbor information.

show running-config

Verifies your configuration entries.

show etherchannel load-balance

Displays the load balance or frame distribution scheme among ports in the port channel.

Related Tasks

Configuring the LACP System Priority (CLI)

Configuring the LACP Port Priority (CLI)

By default, all ports use the same port priority. If the local system has a lower value for the system priority and the system ID than the remote system, you can affect which of the hot-standby links become active first by changing the port priority of LACP EtherChannel ports to a lower value than the default. The hot-standby ports that have lower port numbers become active in the channel first. You can use the show etherchannel summary privileged EXEC command to see which ports are in the hot-standby mode (denoted with an H port-state flag).

Note

If LACP is not able to aggregate all the ports that are compatible (for example, the remote system might have more restrictive hardware limitations), all the ports that cannot be actively included in the EtherChannel are put in the hot-standby state and are used only if one of the channeled ports fails.

Beginning in privileged EXEC mode, follow these steps to configure the LACP port priority. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    lacp port-priority priority

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface gigabitethernet 1/0/2

Specifies the port to be configured, and enters interface configuration mode.

Step 3

lacp port-priority priority

Example:

Controller(config-if)# lacp port-priority 32000

Configures the LACP port priority.

The range is 1 to 65535. The default is 32768. The lower the value, the more likely that the port will be used for LACP transmission.

Step 4

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related Concepts

EtherChannel Configuration Guidelines

Default EtherChannel Configuration

Layer 2 EtherChannel Configuration Guidelines

Related References

Monitoring EtherChannel, PAgP, and LACP Status

EtherChannel Configuration Guidelines

If improperly configured, some EtherChannel ports are automatically disabled to avoid network loops and other problems. Follow these guidelines to avoid configuration problems:

- Configure a PAgP EtherChannel with up to eight Ethernet ports of the same type.

- Configure a LACP EtherChannel with up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

- Configure all ports in an EtherChannel to operate at the same speeds and duplex modes.

- Enable all ports in an EtherChannel. A port in an EtherChannel that is disabled by using the shutdown interface configuration command is treated as a link failure, and its traffic is transferred to one of the remaining ports in the EtherChannel.

- When a group is first created, all ports follow the parameters set for the first port to be added to the group. If you change the configuration of one of these parameters, you must also make the changes to all ports in the group:

- Allowed-VLAN list

- Spanning-tree path cost for each VLAN

- Spanning-tree port priority for each VLAN

- Spanning-tree Port Fast setting

- Do not configure a port to be a member of more than one EtherChannel group.

- Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same controller or on different controllers in the stack. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

- Do not configure a secure port as part of an EtherChannel or the reverse.

- Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

- If EtherChannels are configured on controller interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a controller by using the dot1x system-auth-control global configuration command.

Related Tasks

Configuring the LACP Port Priority (CLI)

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Default EtherChannel Configuration

Feature

Default Setting

Channel groups

None assigned.

Port-channel logical interface

None defined.

PAgP mode

No default.

PAgP learn method

Aggregate-port learning on all ports.

PAgP priority

128 on all ports.

LACP mode

No default.

LACP learn method

Aggregate-port learning on all ports.

LACP port priority

32768 on all ports.

LACP system priority

32768.

LACP system ID

LACP system priority and the controller or stack MAC address.

Load-balancing

Load distribution on the controller is based on the source-MAC address of the incoming packet.

Related Tasks

Configuring the LACP Port Priority (CLI)

Layer 2 EtherChannel Configuration Guidelines

When configuring Layer 2 EtherChannels, follow these guidelines:

- Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with different native VLANs cannot form an EtherChannel.

- An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

- Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

Related Tasks

Configuring the LACP Port Priority (CLI)

Monitoring EtherChannel, PAgP, and LACP Status

You can display EtherChannel, PAgP, and LACP status using the commands listed in this table.

Commands for Monitoring EtherChannel, PAgP, and LACP Status

Command

Description

clear lacp { channel-group-number counters | counters }

Clears LACP channel-group information and traffic counters.

clear pagp { channel-group-number counters | counters }

Clears PAgP channel-group information and traffic counters.

show etherchannel [ channel-group-number { detail | port | port-channel | protocol | summary }] [ detail | load-balance | port | port-channel | protocol | summary ]

Displays EtherChannel information in a brief, detailed, and one-line summary form. Also displays the load-balance or frame-distribution scheme, port, port-channel, and protocol information.

show pagp [ channel-group-number ] { counters | internal | neighbor }

Displays PAgP information such as traffic information, the internal PAgP configuration, and neighbor information.

show pagp [ channel-group-number ] dual-active

Displays the dual-active detection status.

show lacp [ channel-group-number ] { counters | internal  | neighbor | sys-id}

Displays LACP information such as traffic information, the internal LACP configuration, and neighbor information.

show running-config

Verifies your configuration entries.

show etherchannel load-balance

Displays the load balance or frame distribution scheme among ports in the port channel.

Related Tasks

Configuring the LACP Port Priority (CLI)

Configuring the LACP Max Bundle Feature (CLI)

When you specify the maximum number of bundled LACP ports allowed in a port channel, the remaining ports in the port channel are designated as hot-standby ports.

Beginning in privileged EXEC mode, follow these steps to configure the maximum number of LACP ports in a port channel. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface port-channel channel-number

3.    lacp max-bundle max-bundle-number

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface port-channel channel-number

Example:

Controller(config)# interface port-channel 2

Enters interface configuration mode for a port channel.

The range is 1 to 128.

Step 3

lacp max-bundle max-bundle-number

Example:

Controller(config-if)# lacp max-bundle 3

Specifies the maximum number of LACP ports in the port-channel bundle.

The range is 1 to 8.

Step 4

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

LACP and Link Redundancy

Related References

Configuring LACP Hot-Standby Ports: Example

LACP and Link Redundancy

LACP port-channel operation, bandwidth availability, and link redundancy can be further refined with the LACP port-channel min-links and the LACP max-bundle features.

The LACP port-channel min-links feature:

- Configures the minimum number of ports that must be linked up and bundled in the LACP port channel.

- Prevents a low-bandwidth LACP port channel from becoming active.

- Causes an LACP port channel to become inactive if there are too few active members ports to supply the required minimum bandwidth.

The LACP max-bundle feature:

- Defines an upper limit on the number of bundled ports in an LACP port channel.

- Allows hot-standby ports with fewer bundled ports. For example, in an LACP port channel with five ports, you can specify a max-bundle of three, and the two remaining ports are designated as hot-standby ports.

Related Tasks

Configuring the LACP Max Bundle Feature (CLI)

Related References

Configuring LACP Hot-Standby Ports: Example

Configuring LACP Hot-Standby Ports: Example

This example shows how to configure an Etherchannel (port channel 2) that will be active when there are at least three active ports, will comprise up to seven active ports and the remaining ports (up to nine) as hot-standby ports :

Controller# configure terminal
Controller(config)# interface port-channel 2
Controller(config-if)# port-channel min-links 3
Controller(config-if)# lacp max-bundle 7

Related Concepts

LACP and Link Redundancy

Related Tasks

Configuring the LACP Max Bundle Feature (CLI)

Configuring the Port Channel Min-Links Feature (CLI)

You can specify the minimum number of active ports that must be in the link-up state and bundled in an EtherChannel for the port channel interface to transition to the link-up state.

Beginning in privileged EXEC mode, follow these steps to configure the minimum number of links that are required for a port channel. This procedure is optional.

SUMMARY STEPS

1.    configure terminal

2.    interface port-channel channel-number

3.    port-channel min-links min-links-number

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface port-channel channel-number

Example:

Controller(config)# interface port-channel 2

Enters interface configuration mode for a port-channel.

For channel-number, the range is 1 to 128.

Step 3

port-channel min-links min-links-number

Example:

Controller(config-if)# port-channel min-links 3

Specifies the minimum number of member ports that must be in the link-up state and bundled in the EtherChannel for the port channel interface to transition to the link-up state.

For min-links-number , the range is 2 to 8.

Step 4

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

LACP and Link Redundancy

Related References

Configuring LACP Hot-Standby Ports: Example

LACP and Link Redundancy

LACP port-channel operation, bandwidth availability, and link redundancy can be further refined with the LACP port-channel min-links and the LACP max-bundle features.

The LACP port-channel min-links feature:

- Configures the minimum number of ports that must be linked up and bundled in the LACP port channel.

- Prevents a low-bandwidth LACP port channel from becoming active.

- Causes an LACP port channel to become inactive if there are too few active members ports to supply the required minimum bandwidth.

The LACP max-bundle feature:

- Defines an upper limit on the number of bundled ports in an LACP port channel.

- Allows hot-standby ports with fewer bundled ports. For example, in an LACP port channel with five ports, you can specify a max-bundle of three, and the two remaining ports are designated as hot-standby ports.

Related Tasks

Configuring the Port Channel Min-Links Feature (CLI)

Related References

Configuring LACP Hot-Standby Ports: Example

Configuring LACP Hot-Standby Ports: Example

This example shows how to configure an Etherchannel (port channel 2) that will be active when there are at least three active ports, will comprise up to seven active ports and the remaining ports (up to nine) as hot-standby ports :

Controller# configure terminal
Controller(config)# interface port-channel 2
Controller(config-if)# port-channel min-links 3
Controller(config-if)# lacp max-bundle 7

Related Concepts

LACP and Link Redundancy

Related Tasks

Configuring the Port Channel Min-Links Feature (CLI)

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    switchport backup interface interface-id preemption mode [forced | bandwidth | off]

5.    switchport backup interface interface-id preemption delay delay-time

6.    end

7.    show interface [interface-id] switchport backup

8.    copy running-config startup config

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

switchport backup interface interface-id preemption mode [forced | bandwidth | off]

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption mode forced

Configures a preemption mechanism and delay for a Flex Links interface pair. You can configure the preemption as:

- forced—(Optional) The active interface always preempts the backup.

- bandwidth—(Optional) The interface with the higher bandwidth always acts as the active interface.

- off—(Optional) No preemption occurs from active to backup.

Step 5

switchport backup interface interface-id preemption delay delay-time

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption delay 50

Configures the time delay until a port preempts another port.

Note:
Setting a delay time only works with forced and bandwidth modes.

Step 6

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

Step 7

show interface [interface-id] switchport backup

Example:

Controller# show interface gigabitethernet1/0/2 switchport backup

Verifies the configuration.

Step 8

copy running-config startup config

Example:

Controller# copy running-config startup config

(Optional) Saves your entries in the controller startup configuration file.

Related Concepts

Flex Links

Related References

Default Flex Links and MAC Address-Table Move Update Configuration

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring Flex Links: Examples

Configuring Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface
gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

Related Concepts

Flex Links

Related References

Default Flex Links and MAC Address-Table Move Update Configuration

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring Flex Links: Examples

Flex Links

Flex Links are a pair of a Layer 2 interfaces (controller ports or port channels) where one interface is configured to act as a backup to the other. The feature provides an alternative solution to the Spanning Tree Protocol (STP). Users can disable STP and still retain basic link redundancy. Flex Links are typically configured in service provider or enterprise networks where customers do not want to run STP on the controller. If the controller is running STP, Flex Links are not necessary because STP already provides link-level redundancy or backup.

You configure Flex Links on one Layer 2 interface (the active link) by assigning another Layer 2 interface as the Flex Links or backup link. On controllers, the Flex Links can be on the same controller or on another controller in the stack. When one of the links is up and forwarding traffic, the other link is in standby mode, ready to begin forwarding traffic if the other link shuts down. At any given time, only one of the interfaces is in the linkup state and forwarding traffic. If the primary link shuts down, the standby link starts forwarding traffic. When the active link comes back up, it goes into standby mode and does not forward traffic. STP is disabled on Flex Links interfaces.

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links (CLI)

Related References

Configuring Flex Links: Examples

Default Flex Links and MAC Address-Table Move Update Configuration

- Flex Links is not configured, and there are no backup interfaces defined.

- The preemption mode is off.

- The preemption delay is 35 seconds.

- The MAC address-table move update feature is not configured on the controller.

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links (CLI)

Related References

Configuring Flex Links: Examples

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

- Flex Links are supported only on Layer 2 ports and port channels.

- You can configure up to 16 backup links.

- You can configure only one Flex Links backup link for any active link, and it must be a different interface from the active interface.

- An interface can belong to only one Flex Links pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Links pair.

- Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two port channels (EtherChannel logical interfaces) as Flex Links, and you can configure a port channel and a physical interface as Flex Links, with either the port channel or the physical interface as the active link.

- A backup link does not have to be the same type (Gigabit Ethernet or port channel) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link begins to forward traffic.

- STP is disabled on Flex Links ports. A Flex Links port does not participate in STP, even if the VLANs present on the port are configured for STP. When STP is not enabled, be sure that there are no loops in the configured topology.

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links (CLI)

Related References

Configuring Flex Links: Examples

Configuring Flex Links: Examples

This example shows how to verify the configuration after you configure an interface with a backup interface:

Controller# show interface switchport backup

Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/1 GigabitEthernet1/0/2 Active Up/Backup Standby

This example shows how to verify the configuration after you configure the preemption mode as forced for a backup interface pair:

Controller# show interface switchport backup detail

Switch Backup Interface Pairs:

Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/211 GigabitEthernet1/0/2 Active Up/Backup Standby
Interface Pair : Gi1/0/1, Gi1/0/2
Preemption Mode : forced
Preemption Delay : 50 seconds
Bandwidth : 100000 Kbit (Gi1/0/1), 100000 Kbit (Gi1/0/2)
Mac Address Move Update Vlan : auto

Related Concepts

Flex Links

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links (CLI)

Related References

Default Flex Links and MAC Address-Table Move Update Configuration

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    switchport backup interface interface-id preemption mode [forced | bandwidth | off]

5.    switchport backup interface interface-id preemption delay delay-time

6.    end

7.    show interface [interface-id] switchport backup

8.    copy running-config startup config

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

switchport backup interface interface-id preemption mode [forced | bandwidth | off]

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption mode forced

Configures a preemption mechanism and delay for a Flex Links interface pair. You can configure the preemption as:

- forced—(Optional) The active interface always preempts the backup.

- bandwidth—(Optional) The interface with the higher bandwidth always acts as the active interface.

- off—(Optional) No preemption occurs from active to backup.

Step 5

switchport backup interface interface-id preemption delay delay-time

Example:

Controller(conf-if)# switchport backup interface gigabitethernet1/0/2 preemption delay 50

Configures the time delay until a port preempts another port.

Note:
Setting a delay time only works with forced and bandwidth modes.

Step 6

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

Step 7

show interface [interface-id] switchport backup

Example:

Controller# show interface gigabitethernet1/0/2 switchport backup

Verifies the configuration.

Step 8

copy running-config startup config

Example:

Controller# copy running-config startup config

(Optional) Saves your entries in the controller startup configuration file.

Related Concepts

Flex Links Configuration

Related References

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuring Flex Links: Examples

Flex Links Configuration

In the following figure, ports 1 and 2 on controller A are connected to uplink switches B and C. Because they are configured as Flex Links, only one of the interfaces is forwarding traffic; the other is in standby mode. If port 1 is the active link, it begins forwarding traffic between port 1 and switch B; the link between port 2 (the backup link) and switch C is not forwarding traffic. If port 1 goes down, port 2 comes up and starts forwarding traffic to switch C. When port 1 comes back up, it goes into standby mode and does not forward traffic; port 2 continues forwarding traffic.

You can also configure a preemption function, specifying the preferred port for forwarding traffic. For example, you can configure the Flex Links pair with preemption mode. In the scenario shown, when port 1 comes back up and has more bandwidth than port 2, port 1 begins forwarding traffic after 60 seconds. Port 2 becomes the standby port. You do this by entering the switchport backup interface preemption mode bandwidth and switchport backup interface preemption delay interface configuration commands.

Flex Links Configuration Example

If a primary (forwarding) link goes down, a trap notifies the network management stations. If the standby link goes down, a trap notifies the users.

Flex Links are supported only on Layer 2 ports and port channels, not on VLANs or on Layer 3 ports.

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links: Examples

This example shows how to verify the configuration after you configure an interface with a backup interface:

Controller# show interface switchport backup

Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/1 GigabitEthernet1/0/2 Active Up/Backup Standby

This example shows how to verify the configuration after you configure the preemption mode as forced for a backup interface pair:

Controller# show interface switchport backup detail

Switch Backup Interface Pairs:

Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/211 GigabitEthernet1/0/2 Active Up/Backup Standby
Interface Pair : Gi1/0/1, Gi1/0/2
Preemption Mode : forced
Preemption Delay : 50 seconds
Bandwidth : 100000 Kbit (Gi1/0/1), 100000 Kbit (Gi1/0/2)
Mac Address Move Update Vlan : auto

Related Tasks

Configuring a Preemption Scheme for a Pair of Flex Links (CLI)

Configuring Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(conf)# interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id

Example:

Controller(conf-if)# switchport backup interface
gigabitethernet1/0/2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface. When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(conf-if)# end

Returns to privileged EXEC mode.

Related Concepts

Flex Links Configuration

Related References

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuring Flex Links: Examples

Flex Links Configuration

In the following figure, ports 1 and 2 on controller A are connected to uplink switches B and C. Because they are configured as Flex Links, only one of the interfaces is forwarding traffic; the other is in standby mode. If port 1 is the active link, it begins forwarding traffic between port 1 and switch B; the link between port 2 (the backup link) and switch C is not forwarding traffic. If port 1 goes down, port 2 comes up and starts forwarding traffic to switch C. When port 1 comes back up, it goes into standby mode and does not forward traffic; port 2 continues forwarding traffic.

You can also configure a preemption function, specifying the preferred port for forwarding traffic. For example, you can configure the Flex Links pair with preemption mode. In the scenario shown, when port 1 comes back up and has more bandwidth than port 2, port 1 begins forwarding traffic after 60 seconds. Port 2 becomes the standby port. You do this by entering the switchport backup interface preemption mode bandwidth and switchport backup interface preemption delay interface configuration commands.

Flex Links Configuration Example

If a primary (forwarding) link goes down, a trap notifies the network management stations. If the standby link goes down, a trap notifies the users.

Flex Links are supported only on Layer 2 ports and port channels, not on VLANs or on Layer 3 ports.

Related Tasks

Configuring Flex Links (CLI)

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Related Tasks

Configuring Flex Links (CLI)

Configuring Flex Links: Examples

This example shows how to verify the configuration after you configure an interface with a backup interface:

Controller# show interface switchport backup

Switch Backup Interface Pairs:
Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/1 GigabitEthernet1/0/2 Active Up/Backup Standby

This example shows how to verify the configuration after you configure the preemption mode as forced for a backup interface pair:

Controller# show interface switchport backup detail

Switch Backup Interface Pairs:

Active Interface Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/211 GigabitEthernet1/0/2 Active Up/Backup Standby
Interface Pair : Gi1/0/1, Gi1/0/2
Preemption Mode : forced
Preemption Delay : 50 seconds
Bandwidth : 100000 Kbit (Gi1/0/1), 100000 Kbit (Gi1/0/2)
Mac Address Move Update Vlan : auto

Related Tasks

Configuring Flex Links (CLI)

Configuring VLAN Load Balancing on Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id prefer vlan vlan-range

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller (config)# interface gigabitethernet2/0/6

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id prefer vlan vlan-range

Example:

Controller (config-if)# switchport backup interface
gigabitethernet2/0/8 prefer vlan 2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface and specifies the VLANs carried on the interface. The VLAN ID range is 1 to 4094.

Step 4

end

Example:

Controller (config-if)# end

Returns to privileged EXEC mode.

Related References

Flex Links VLAN Load Balancing Configuration Guidelines

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring VLAN Load Balancing on Flex Links: Examples

Flex Links VLAN Load Balancing Configuration Guidelines

- For Flex Links VLAN load balancing, you must choose the preferred VLANs on the backup interface.

- You cannot configure a preemption mechanism and VLAN load balancing for the same Flex Links pair.

Related Tasks

Configuring VLAN Load Balancing on Flex Links (CLI)

Related References

Configuring VLAN Load Balancing on Flex Links: Examples

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

- Flex Links are supported only on Layer 2 ports and port channels.

- You can configure up to 16 backup links.

- You can configure only one Flex Links backup link for any active link, and it must be a different interface from the active interface.

- An interface can belong to only one Flex Links pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Links pair.

- Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two port channels (EtherChannel logical interfaces) as Flex Links, and you can configure a port channel and a physical interface as Flex Links, with either the port channel or the physical interface as the active link.

- A backup link does not have to be the same type (Gigabit Ethernet or port channel) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link begins to forward traffic.

- STP is disabled on Flex Links ports. A Flex Links port does not participate in STP, even if the VLANs present on the port are configured for STP. When STP is not enabled, be sure that there are no loops in the configured topology.

Related Tasks

Configuring VLAN Load Balancing on Flex Links (CLI)

Related References

Configuring VLAN Load Balancing on Flex Links: Examples

Configuring VLAN Load Balancing on Flex Links: Examples

In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the controller:

Controller(config)# interface gigabitethernet 2/0/6
Controller(config-if)# switchport backup interface gigabitethernet 2/0/8 prefer vlan 60,100-120

When both interfaces are up, Gi2/0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi2/0/6 forwards traffic for VLANs 1 to 50.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface goes down (LINK_DOWN), VLANs preferred on this interface are moved to the peer interface of the Flex Links pair. In this example, if interface Gi2/0/6 goes down, Gi2/0/8 carries all VLANs of the Flex Links pair.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Down/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface comes up, VLANs preferred on this interface are blocked on the peer interface and moved to the forwarding state on the interface that has just come up. In this example, if interface Gi2/0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi2/0/8 and forwarded on Gi2/0/6.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

Controller# show interfaces switchport backup detail

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
FastEthernet1/0/3       FastEthernet1/0/4       Active Down/Backup Up

Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Preemption Mode  : off
Bandwidth : 10000 Kbit (Fa1/0/3), 100000 Kbit (Fa1/0/4)
Mac Address Move Update Vlan : auto

Related Tasks

Configuring VLAN Load Balancing on Flex Links (CLI)

Related References

Flex Links VLAN Load Balancing Configuration Guidelines

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring VLAN Load Balancing on Flex Links (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    switchport backup interface interface-id prefer vlan vlan-range

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller (config)# interface gigabitethernet2/0/6

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

switchport backup interface interface-id prefer vlan vlan-range

Example:

Controller (config-if)# switchport backup interface
gigabitethernet2/0/8 prefer vlan 2

Configures a physical Layer 2 interface (or port channel) as part of a Flex Links pair with the interface and specifies the VLANs carried on the interface. The VLAN ID range is 1 to 4094.

Step 4

end

Example:

Controller (config-if)# end

Returns to privileged EXEC mode.

Related References

Configuring VLAN Load Balancing on Flex Links: Examples

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuring VLAN Load Balancing on Flex Links: Examples

In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the controller:

Controller(config)# interface gigabitethernet 2/0/6
Controller(config-if)# switchport backup interface gigabitethernet 2/0/8 prefer vlan 60,100-120

When both interfaces are up, Gi2/0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi2/0/6 forwards traffic for VLANs 1 to 50.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface goes down (LINK_DOWN), VLANs preferred on this interface are moved to the peer interface of the Flex Links pair. In this example, if interface Gi2/0/6 goes down, Gi2/0/8 carries all VLANs of the Flex Links pair.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Down/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Links interface comes up, VLANs preferred on this interface are blocked on the peer interface and moved to the forwarding state on the interface that has just come up. In this example, if interface Gi2/0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi2/0/8 and forwarded on Gi2/0/6.

Controller# show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet2/0/6    GigabitEthernet2/0/8    Active Up/Backup Standby

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

Controller# show interfaces switchport backup detail

Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
FastEthernet1/0/3       FastEthernet1/0/4       Active Down/Backup Up

Vlans Preferred on Active Interface: 1-2,5-4094
Vlans Preferred on Backup Interface: 3-4
Preemption Mode  : off
Bandwidth : 10000 Kbit (Fa1/0/3), 100000 Kbit (Fa1/0/4)
Mac Address Move Update Vlan : auto

Related Tasks

Configuring VLAN Load Balancing on Flex Links (CLI)

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Configuring MAC Address-Table Move Update (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

4.    end

5.    mac address-table move update transmit

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller#interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

Example:

Controller(config-if)# switchport backup interface
gigabitethernet0/2 mmu primary vlan 2

Configures a physical Layer 2 interface (or port channel), as part of a Flex Links pair with the interface. The MAC address-table move update VLAN is the lowest VLAN ID on the interface.

Configure a physical Layer 2 interface (or port channel) and specifies the VLAN ID on the interface, which is used for sending the MAC address-table move update.

When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(config-if)# end

Returns to global configuration mode.

Step 5

mac address-table move update transmit

Example:

Controller(config)#
mac address-table move update
transmit

Enables the access controller to send MAC address-table move updates to other controllers in the network if the primary link goes down and the controller starts forwarding traffic through the standby link.

Step 6

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related References

Configuring the MAC Address-Table Move Update: Examples

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuring the MAC Address-Table Move Update: Examples

This example shows how to verify the configuration after you configure an access controller to send MAC address-table move updates:

Controller# show mac address-table move update

Switch-ID : 010b.4630.1780
Dst mac-address : 0180.c200.0010
Vlans/Macs supported : 1023/8320
Default/Current settings: Rcv Off/On, Xmt Off/On
Max packets per min : Rcv 40, Xmt 60
Rcv packet count : 5
Rcv conforming packet count : 5
Rcv invalid packet count : 0
Rcv packet count this min : 0
Rcv threshold exceed count : 0
Rcv last sequence# this min : 0
Rcv last interface : Po2
Rcv last src-mac-address : 000b.462d.c502
Rcv last switch-ID : 0403.fd6a.8700
Xmt packet count : 0
Xmt packet count this min : 0
Xmt threshold exceed count : 0
Xmt pak buf unavail cnt : 0
Xmt last interface : None

Related Tasks

Configuring MAC Address-Table Move Update (CLI)

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

SUMMARY STEPS

1.    configure terminal

2.    mac address-table move update receive

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

mac address-table move update receive

Example:

Controller (config)# mac address-table move update receive

Enables the controller to obtain and processes the MAC address-table move updates.

Step 3

end

Example:

Controller (config)# end

Returns to privileged EXEC mode.

Related References

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Configuring the MAC Address-Table Move Update: Examples

Monitoring Flex Links, Multicast Fast Convergence, and MAC Address-Table Move Update

Command

Purpose

show interface [interface-id] switchport backup

Displays the Flex Links backup interface configured for an interface or all the configured Flex Links and the state of each active and backup interface (up or standby mode).

show ip igmp profile address-table move update profile-id

Displays the specified IGMP profile or all the IGMP profiles defined on the controller.

show mac address-table move update

Displays the MAC address-table move update information on the controller.

Configuring the MAC Address-Table Move Update: Examples

This example shows how to verify the configuration after you configure an access controller to send MAC address-table move updates:

Controller# show mac address-table move update

Switch-ID : 010b.4630.1780
Dst mac-address : 0180.c200.0010
Vlans/Macs supported : 1023/8320
Default/Current settings: Rcv Off/On, Xmt Off/On
Max packets per min : Rcv 40, Xmt 60
Rcv packet count : 5
Rcv conforming packet count : 5
Rcv invalid packet count : 0
Rcv packet count this min : 0
Rcv threshold exceed count : 0
Rcv last sequence# this min : 0
Rcv last interface : Po2
Rcv last src-mac-address : 000b.462d.c502
Rcv last switch-ID : 0403.fd6a.8700
Xmt packet count : 0
Xmt packet count this min : 0
Xmt threshold exceed count : 0
Xmt pak buf unavail cnt : 0
Xmt last interface : None

Related Tasks

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

SUMMARY STEPS

1.    configure terminal

2.    mac address-table move update receive

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode

Step 2

mac address-table move update receive

Example:

Controller (config)# mac address-table move update receive

Enables the controller to obtain and processes the MAC address-table move updates.

Step 3

end

Example:

Controller (config)# end

Returns to privileged EXEC mode.

Related Concepts

MAC Address-Table Move Update

Related References

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring the MAC Address-Table Move Update: Examples

Configuring MAC Address-Table Move Update (CLI)

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

4.    end

5.    mac address-table move update transmit

6.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller#interface gigabitethernet1/0/1

Specifies the interface, and enters interface configuration mode. The interface can be a physical Layer 2 interface or a port channel (logical interface).

Step 3

Use one of the following:

- switchport backup interface interface-id

- switchport backup interface interface-id mmu primary vlan vlan-id

Example:

Controller(config-if)# switchport backup interface
gigabitethernet0/2 mmu primary vlan 2

Configures a physical Layer 2 interface (or port channel), as part of a Flex Links pair with the interface. The MAC address-table move update VLAN is the lowest VLAN ID on the interface.

Configure a physical Layer 2 interface (or port channel) and specifies the VLAN ID on the interface, which is used for sending the MAC address-table move update.

When one link is forwarding traffic, the other interface is in standby mode.

Step 4

end

Example:

Controller(config-if)# end

Returns to global configuration mode.

Step 5

mac address-table move update transmit

Example:

Controller(config)#
mac address-table move update
transmit

Enables the access controller to send MAC address-table move updates to other controllers in the network if the primary link goes down and the controller starts forwarding traffic through the standby link.

Step 6

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

MAC Address-Table Move Update

Related References

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Configuring the MAC Address-Table Move Update: Examples

MAC Address-Table Move Update

The MAC address-table move update feature allows the controller to provide rapid bidirectional convergence when a primary (forwarding) link goes down and the standby link begins forwarding traffic.

MAC Address-Table Move Update Example. In the following figure, the controller and switches B and C form the Flexlink through a Flex Links pair. Port 3 is forwarding traffic, and port 4 is in the backup state. Switch A is an access switch, and ports 1 and 2 on switch A are connected to uplink switches B and C. The MAC addresses of the wireless clients have been learnt on port 1 of the switch A.

In the above figure, three wireless clients connect to an access point and communicate to the controller. The PC connected to switch A communicates with the wireless clients through the data path from port 3 to port 1. If the MAC address-table move update feature is not configured on the controller and port 3 goes down, port 4 starts forwarding traffic. However, for a short time the wireless clients will not be able to pass any traffic to the PC as port 3 is down.

If the MAC address-table move update feature is configured and enabled on the controller, and port 3 goes down, the controller sends a MAC address-table move update packet (MMU) from port 4. This MMU packet carries all the MAC addresses of the wireless clients. Switch C gets this packet on port 4 and immediately learns the MAC addresses of the wireless clients, which reduces the reconvergence time. The PC transmits data to the wireless clients using the path from port 2 to port 4. Switch C also bridges the same MMU packet in the VLAN so that all the switches in the network will update the MAC address table to ensure that the next packet to any wireless client towards controller comes on the right path. The controller learns only the MAC addresses of the wireless clients.

Related Tasks

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Configuring MAC Address-Table Move Update (CLI)

Related References

Configuring the MAC Address-Table Move Update: Examples

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

- Flex Links are supported only on Layer 2 ports and port channels.

- You can configure up to 16 backup links.

- You can configure only one Flex Links backup link for any active link, and it must be a different interface from the active interface.

- An interface can belong to only one Flex Links pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Links pair.

- Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two port channels (EtherChannel logical interfaces) as Flex Links, and you can configure a port channel and a physical interface as Flex Links, with either the port channel or the physical interface as the active link.

- A backup link does not have to be the same type (Gigabit Ethernet or port channel) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link begins to forward traffic.

- STP is disabled on Flex Links ports. A Flex Links port does not participate in STP, even if the VLANs present on the port are configured for STP. When STP is not enabled, be sure that there are no loops in the configured topology.

Related Tasks

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Configuring MAC Address-Table Move Update (CLI)

Related References

Configuring the MAC Address-Table Move Update: Examples

Configuring the MAC Address-Table Move Update: Examples

This example shows how to verify the configuration after you configure an access controller to send MAC address-table move updates:

Controller# show mac address-table move update

Switch-ID : 010b.4630.1780
Dst mac-address : 0180.c200.0010
Vlans/Macs supported : 1023/8320
Default/Current settings: Rcv Off/On, Xmt Off/On
Max packets per min : Rcv 40, Xmt 60
Rcv packet count : 5
Rcv conforming packet count : 5
Rcv invalid packet count : 0
Rcv packet count this min : 0
Rcv threshold exceed count : 0
Rcv last sequence# this min : 0
Rcv last interface : Po2
Rcv last src-mac-address : 000b.462d.c502
Rcv last switch-ID : 0403.fd6a.8700
Xmt packet count : 0
Xmt packet count this min : 0
Xmt threshold exceed count : 0
Xmt pak buf unavail cnt : 0
Xmt last interface : None

Related Concepts

MAC Address-Table Move Update

Related Tasks

Configuring a Controller to Obtain and Process MAC Address-Table Move Update Messages (CLI)

Configuring MAC Address-Table Move Update (CLI)

Related References

Restrictions for Configuring Flex Links and MAC Address-Table Move Update

Multicast Fast Convergence with Flex Links Failover

Multicast fast convergence reduces the multicast traffic convergence time after a Flex Links failure. Multicast fast convergence is implemented by a combination of learning the backup link as an mrouter port, generating IGMP reports, and leaking IGMP reports.

Related References

Configuring Multicast Fast Convergence with Flex Links Failover: Examples

Configuring Multicast Fast Convergence with Flex Links Failover: Examples

These are configuration examples for learning the other Flex Links port as the mrouter port when Flex Links is configured on GigabitEthernet1/0/11 and GigabitEthernet1/0/12, and output for the show interfaces switchport backup command:

Controller# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Controller(config)# interface GigabitEthernet1/0/11
Controller(config-if)# switchport trunk encapsulation dot1q
Controller(config-if)# switchport mode trunk
Controller(config-if)# switchport backup interface GigabitEthernet1/0/12
Controller(config-if)# exit
Controller(config)# interface GigabitEthernet1/0/12
Controller(config-if)# switchport trunk encapsulation dot1q
Controller(config-if)# switchport mode trunk
Controller(config-if)# end
Controller# show interfaces switchport backup detail
Switch Backup Interface Pairs:
Active Interface Backup Interface State
GigabitEthernet1/0/11 GigabitEthernet1/0/12 Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : Off
Bandwidth : 100000 Kbit (Gi1/0/11), 100000 Kbit (Gi1/0/12)
Mac Address Move Update Vlan : auto

This output shows a querier for VLANs 1 and 401, with their queries reaching the controller through GigabitEthernet1/0/11:

Controller# show ip igmp snooping querier

Vlan         IP Address                 IGMP Version                     Port
-------------------------------------------------------------
1           1.1.1.1                   v2                     Gi1/0/11
401         41.41.41.1                 v2                     Gi1/0/11

This example is output for the show ip igmp snooping mrouter command for VLANs 1 and 401:

Controller# show ip igmp snooping mrouter

Vlan         ports
----         -----
1          Gi1/0/11(dynamic), Gi1/0/12(dynamic)
401         Gi1/0/11(dynamic), Gi1/0/12(dynamic)

Similarly, both Flex Links ports are part of learned groups. In this example, GigabitEthernet2/0/11 is a receiver/host in VLAN 1, which is interested in two multicast groups:

Controller# show ip igmp snooping groups

Vlan         Group             Type         Version             Port List
-----------------------------------------------------------------------
1         228.1.5.1             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11
1         228.1.5.2             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11

When a host responds to the general query, the controller forwards this report on all the mrouter ports. In this example, when a host sends a report for the group 228.1.5.1, it is forwarded only on GigabitEthernet1/0/11, because the backup port GigabitEthernet1/0/12 is blocked. When the active link, GigabitEthernet1/0/11, goes down, the backup port, GigabitEthernet1/0/12, begins forwarding.

As soon as this port starts forwarding, the controller sends proxy reports for the groups 228.1.5.1 and 228.1.5.2 on behalf of the host. The upstream router learns the groups and starts forwarding multicast data. This is the default behavior of Flex Links. This behavior changes when the user configures fast convergence using the switchport backup interface gigabitEthernet 1/0/12 multicast fast-convergence command. This example shows turning on this feature:

Controller# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Controller(config)# interface gigabitEthernet 1/0/11
Controller(config-if)# switchport backup interface gigabitEthernet 1/0/12 multicast fast-convergence
Controller(config-if)# exit
Controller# show interfaces switchport backup detail

Switch Backup Interface Pairs:
Active                         Interface                         Backup Interface State
------------------------------------------------------------------------
GigabitEthernet1/0/11     GigabitEthernet1/0/12     Active Up/Backup Standby
Preemption Mode : off
Multicast Fast Convergence : On
Bandwidth : 100000 Kbit (Gi1/0/11), 100000 Kbit (Gi1/0/12)
Mac Address Move Update Vlan : auto

This output shows a querier for VLAN 1 and 401 with their queries reaching the controller through GigabitEthernet1/0/11:

Controller# show ip igmp snooping querier

Vlan             IP Address                 IGMP Version                 Port
-------------------------------------------------------------
1              1.1.1.1                   v2                 Gi1/0/11
401             41.41.41.1                 v2                 Gi1/0/11

This is output for the show ip igmp snooping mrouter command for VLAN 1 and 401:

Controller# show ip igmp snooping mrouter

Vlan             ports
----             -----
1             Gi1/0/11(dynamic), Gi1/0/12(dynamic)
401             Gi1/0/11(dynamic), Gi1/0/12(dynamic)

Similarly, both the Flex Links ports are a part of the learned groups. In this example, GigabitEthernet2/0/11 is a receiver/host in VLAN 1, which is interested in two multicast groups:

Controller# show ip igmp snooping groups

Vlan         Group             Type         Version             Port List
-----------------------------------------------------------------------
1         228.1.5.1             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11
1         228.1.5.2             igmp         v2             Gi1/0/11, Gi1/0/12, Gi2/0/11

Whenever a host responds to the general query, the controller forwards this report on all the mrouter ports. When you turn on this feature through the command-line port, and when a report is forwarded by the controller on GigabitEthernet1/0/11, it is also leaked to the backup port GigabitEthernet1/0/12. The upstream router learns the groups and starts forwarding multicast data, which is dropped at the ingress because GigabitEthernet1/0/12 is blocked. When the active link, GigabitEthernet1/0/11, goes down, the backup port, GigabitEthernet1/0/12, begins forwarding. You do not need to send any proxy reports as the multicast data is already being forwarded by the upstream router. By leaking reports to the backup port, a redundant multicast path has been set up, and the time taken for the multicast traffic convergence is very minimal.

Related Concepts

Multicast Fast Convergence with Flex Links Failover

Enabling UDLD Globally (CLI)

Follow these steps to enable UDLD in the aggressive or normal mode and to set the configurable message timer on all fiber-optic ports on the controller.

SUMMARY STEPS

1.    configure terminal

2.    udld {aggressive | enable | message time message-timer-interval}

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

udld {aggressive | enable | message time message-timer-interval}

Example:

Controller(config)# udld enable
message time 10

Specifies the UDLD mode of operation:

- aggressive—Enables UDLD in aggressive mode on all fiber-optic ports.

- enable—Enables UDLD in normal mode on all fiber-optic ports on the controller. UDLD is disabled by default. An individual interface configuration overrides the setting of the udld enable global configuration command.

- message time message-timer-interval—Configures the period of time between UDLD probe messages on ports that are in the advertisement phase and are detected to be bidirectional. The range is from 1 to 90 seconds; the default value is 15.
Note:
This command affects fiber-optic ports only. Use the udld interface configuration command to enable UDLD on other port types.

Use the no form of this command, to disable UDLD.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related References

Monitoring and Maintaing UDLD

Enabling UDLD on an Interface (CLI)

Follow these steps either to enable UDLD in the aggressive or normal mode or to disable UDLD on a port.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    udld port [aggressive]

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface
gigabitethernet 1/0/1

Specifies the port to be enabled for UDLD, and enters interface configuration mode.

Step 3

udld port [aggressive]

Example:

Controller(config-if)# udld port aggressive

UDLD is disabled by default.

- udld port—Enables UDLD in normal mode on the specified port.

- udld port aggressive—(Optional) Enables UDLD in aggressive mode on the specified port.

Note:
Use the no udld port interface configuration command to disable UDLD on a specified fiber-optic port.

Step 4

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related References

Monitoring and Maintaing UDLD

Monitoring and Maintaing UDLD

To monitor the UDLD status for the specified port or for all ports, use the show udld [interface-id] privileged EXEC command.

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Enabling UDLD Globally (CLI)

Follow these steps to enable UDLD in the aggressive or normal mode and to set the configurable message timer on all fiber-optic ports on the controller.

SUMMARY STEPS

1.    configure terminal

2.    udld {aggressive | enable | message time message-timer-interval}

3.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

udld {aggressive | enable | message time message-timer-interval}

Example:

Controller(config)# udld enable
message time 10

Specifies the UDLD mode of operation:

- aggressive—Enables UDLD in aggressive mode on all fiber-optic ports.

- enable—Enables UDLD in normal mode on all fiber-optic ports on the controller. UDLD is disabled by default. An individual interface configuration overrides the setting of the udld enable global configuration command.

- message time message-timer-interval—Configures the period of time between UDLD probe messages on ports that are in the advertisement phase and are detected to be bidirectional. The range is from 1 to 90 seconds; the default value is 15.
Note:
This command affects fiber-optic ports only. Use the udld interface configuration command to enable UDLD on other port types.

Use the no form of this command, to disable UDLD.

Step 3

end

Example:

Controller(config)# end

Returns to privileged EXEC mode.

Related Concepts

Aggressive Mode

Normal Mode

Methods to Detect Unidirectional Links

Event-Driven Detection and Echoing

Related References

UDLD Reset Options

Default UDLD Configuration

Enabling UDLD on an Interface (CLI)

Follow these steps either to enable UDLD in the aggressive or normal mode or to disable UDLD on a port.

SUMMARY STEPS

1.    configure terminal

2.    interface interface-id

3.    udld port [aggressive]

4.    end

DETAILED STEPS

Command or Action

Purpose

Step 1

configure terminal

Example:

Controller# configure terminal

Enters global configuration mode.

Step 2

interface interface-id

Example:

Controller(config)# interface
gigabitethernet 1/0/1

Specifies the port to be enabled for UDLD, and enters interface configuration mode.

Step 3

udld port [aggressive]

Example:

Controller(config-if)# udld port aggressive

UDLD is disabled by default.

- udld port—Enables UDLD in normal mode on the specified port.

- udld port aggressive—(Optional) Enables UDLD in aggressive mode on the specified port.

Note:
Use the no udld port interface configuration command to disable UDLD on a specified fiber-optic port.

Step 4

end

Example:

Controller(config-if)# end

Returns to privileged EXEC mode.

Related Concepts

Aggressive Mode

Normal Mode

Methods to Detect Unidirectional Links

Event-Driven Detection and Echoing

Related References

UDLD Reset Options

Default UDLD Configuration

Aggressive Mode

In aggressive mode, UDLD detects a unidirectional link by using the previous detection methods. UDLD in aggressive mode can also detect a unidirectional link on a point-to-point link on which no failure between the two devices is allowed. It can also detect a unidirectional link when one of these problems exists:

- On fiber-optic or twisted-pair links, one of the ports cannot send or receive traffic.

- On fiber-optic or twisted-pair links, one of the ports is down while the other is up.

- One of the fiber strands in the cable is disconnected.

In these cases, UDLD disables the affected port.

In a point-to-point link, UDLD hello packets can be considered as a heart beat whose presence guarantees the health of the link. Conversely, the loss of the heart beat means that the link must be shut down if it is not possible to reestablish a bidirectional link.

If both fiber strands in a cable are working normally from a Layer 1 perspective, UDLD in aggressive mode detects whether those fiber strands 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.

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Normal Mode

In normal mode, UDLD detects a unidirectional link when fiber strands in a fiber-optic port are misconnected and the Layer 1 mechanisms do not detect this misconnection. If the ports are connected correctly but the traffic is one way, UDLD does not detect the unidirectional link because the Layer 1 mechanism, which is supposed to detect this condition, does not do so. In this case, the logical link is considered undetermined, and UDLD does not disable the port.

When UDLD is in normal mode, if one of the fiber strands in a pair is disconnected, as long as autonegotiation is active, the link does not stay up because the Layer 1 mechanisms detects a physical problem with the link. In this case, UDLD does not take any action and the logical link is considered undetermined.

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Methods to Detect Unidirectional Links

UDLD operates by using two methods:

- Neighbor database maintenance

- Event-driven detection and echoing

- Event-Driven Detection and Echoing

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Event-Driven Detection and Echoing

UDLD relies on echoing as its detection operation. Whenever a UDLD device learns about a new neighbor or receives a resynchronization request from an out-of-sync neighbor, it restarts the detection window on its side of the connection and sends echo messages in reply. Because this behavior is the same on all UDLD neighbors, the sender of the echoes expects to receive an echo in reply.

If the detection window ends and no valid reply message is received, the link might shut down, depending on the UDLD mode. When UDLD is in normal mode, the link might be considered undetermined and might not be shut down. When UDLD is in aggressive mode, the link is considered unidirectional, and the port is disabled.

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

UDLD Reset Options

If an interface becomes disabled by UDLD, you can use one of the following options to reset UDLD:

- The udld reset interface configuration command.

- The shutdown interface configuration command followed by the no shutdown interface configuration command restarts the disabled port.

- The no udld {aggressive | enable} global configuration command followed by the udld {aggressive | enable} global configuration command reenables the disabled ports.

- The no udld port interface configuration command followed by the udld port [aggressive] interface configuration command reenables the disabled fiber-optic port.

- The errdisable recovery cause udld global configuration command enables the timer to automatically recover from the UDLD error-disabled state, and the errdisable recovery interval interval global configuration command specifies the time to recover from the UDLD error-disabled state.

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)

Default UDLD Configuration

Default UDLD Configuration

Feature

Default Setting

UDLD global enable state

Globally disabled

UDLD per-port enable state for fiber-optic media

Disabled on all Ethernet fiber-optic ports

UDLD per-port enable state for twisted-pair (copper) media

Disabled on all Ethernet 10/100 and 1000BASE-TX ports

UDLD aggressive mode

Disabled

Related Tasks

Enabling UDLD Globally (CLI)

Enabling UDLD on an Interface (CLI)