Cisco Nexus 4001I and 4005I Switch Module for IBM BladeCenter NX-OS Configuration Guide
Configuring EtherChannels
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Configuring EtherChannels

Table Of Contents

Configuring EtherChannels

Information About EtherChannels

Understanding EtherChannels

Compatibility Requirements

Load Balancing Using EtherChannels

Understanding LACP

LACP Overview

LACP ID Parameters

Port-Channel Modes

LACP Marker Responders

LACP-Enabled and Static EtherChannels Differences

Configuring EtherChannels

Creating an EtherChannel

Adding a Port to an EtherChannel

Configuring Load Balancing Using EtherChannels

Enabling LACP

Configuring Port-Channel Port Modes

Configuring the LACP System Priority and System ID

Configuring the LACP Port Priority

Verifying Port-Channel Configuration


Configuring EtherChannels


This chapter describes how to configure EtherChannels and to apply and configure the Link Aggregation Control Protocol (LACP) for more efficient use of EtherChannels in Cisco NX-OS software.

This chapter includes the following sections:

Information About EtherChannels

Configuring EtherChannels

Verifying Port-Channel Configuration

Information About EtherChannels

An EtherChannel bundles up to eight individual interfaces into a group to provide increased bandwidth and redundancy. Port channeling also load balances traffic across these physical interfaces. The EtherChannel stays operational as long as at least one physical interface within the EtherChannel is operational.

You create an EtherChannel by bundling compatible interfaces. You can configure and run either static EtherChannels or EtherChannels running the Link Aggregation Control Protocol (LACP). (See "Understanding LACP" section for information on LACP.)

Any configuration changes that you apply to the EtherChannel are applied to each member interface of that EtherChannel. For example, if you configure Spanning Tree Protocol (STP) parameters on the EtherChannel, the Cisco NX-OS applies those parameters to each interface in the EtherChannel.

You can use static EtherChannels, with no associated protocol, for a simplified configuration. For more efficient use of the EtherChannel, you can use the Link Aggregation Control Protocol (LACP), which is defined in IEEE 802.3ad. When you use LACP, the link passes protocol packets.

This section includes the following topics:

Understanding EtherChannels

Compatibility Requirements

Load Balancing Using EtherChannels

Understanding LACP

Understanding EtherChannels

Using EtherChannels, Cisco NX-OS provides wider bandwidth, redundancy, and load balancing across the channels.

You can collect up to eight ports into a static EtherChannel or you can enable the Link Aggregation Control Protocol (LACP). Configuring EtherChannels with LACP requires slightly different steps than configuring static EtherChannels (see the "Configuring EtherChannels" section).


Note Cisco NX-OS does not support Port Aggregation Protocol (PAgP) for EtherChannels.


An EtherChannel bundles individual links into a channel group to create a single logical link that provides the aggregate bandwidth of up to eight physical links. If a member port within an EtherChannel fails, traffic previously carried over the failed link switches to the remaining member ports within the EtherChannel.

Each port can be in only one EtherChannel. All the ports in an EtherChannel must be compatible; they must use the same speed and operate in full-duplex mode (see the "Compatibility Requirements" section). When you are running static EtherChannels, without LACP, the individual links are all in the on channel mode; you cannot change this mode without enabling LACP (see the "Port-Channel Modes" section).


Note You cannot change the mode from ON to Active or from ON to Passive.


You can create an EtherChannel directly by creating the port-channel interface, or you can create a channel group that acts to aggregate individual ports into a bundle. When you associate an interface with a channel group, Cisco NX-OS creates a matching EtherChannel automatically if the EtherChannel does not already exist. You can also create the EtherChannel first. In this instance, Cisco NX-OS creates an empty channel group with the same channel number as the EtherChannel and takes the default configuration.


Note The EtherChannel is operationally up when at least one of the member ports is up and the status of that port is channeling. The EtherChannel is operationally down when all member ports are operationally down.


Compatibility Requirements

When you add an interface to a channel group, Cisco NX-OS checks certain interface attributes to ensure that the interface is compatible with the channel group. Cisco NX-OS also checks a number of operational attributes for an interface before allowing that interface to participate in the port-channel aggregation.

The compatibility check includes the following operational attributes:

Port mode

Access VLAN

Trunk native VLAN

Allowed VLAN list

Speed

802.3x flow control setting

MTU

The switch only supports system level MTU. This attribute cannot be changed on an individual port basis.

Broadcast/Unicast/Multicast Storm Control setting

Priority-Flow-Control

Untagged CoS

Use the show port-channel compatibility-parameters command to see the full list of compatibility checks that Cisco NX-OS uses.

You can only add interfaces configured with the channel mode set to on to static EtherChannels. You can also only add interfaces configured with the channel mode as active or passive to EtherChannels that are running LACP. (See the "Port-Channel Modes" section for information on port-channel modes.) You can configure these attributes on an individual member port.

When the interface joins an EtherChannel, the following individual parameters are replaced with the values on the EtherChannel:

Bandwidth

MAC address

Spanning Tree Protocol

The following interface parameters remain unaffected when the interface joins an EtherChannel:

Description

CDP

LACP port priority

Debounce

Load Balancing Using EtherChannels

Cisco NX-OS load balances traffic across all operational interfaces in an EtherChannel 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. EtherChannels provide load balancing by default and the basic configuration uses the following criteria to select the link:

For a Layer 2 frame, it uses the source and destination MAC addresses.

For a Layer 3 frame, it uses the source and destination MAC addresses and the source and destination IP addresses.

For a Layer 4 frame, it uses the source and destination MAC addresses, the source and destination IP addresses, and the source and destination port number.

You can configure the switch to use one of the following methods to load balance across the EtherChannel:

Destination MAC address

Source MAC address

Source and destination MAC address

Destination IP address

Source IP address

Source and destination IP address

Destination TCP/UDP port number

Source TCP/UDP port number

Source and destination TCP/UDP port number

Table 11-1 shows the criteria used for each configuration:

Table 11-1 EtherChannel Load-Balancing Criteria

Configuration
Layer 2 Criteria
Layer 3 Criteria
Layer 4 Criteria

Destination MAC

Destination MAC

Destination MAC

Destination MAC

Source MAC

Source MAC

Source MAC

Source MAC

Source and destination MAC

Source and destination MAC

Source and destination MAC

Source and destination MAC

Destination IP

Destination MAC

Destination MAC, destination IP

Destination MAC, destination IP

Source IP

Source MAC

Source MAC, source IP

Source MAC, source IP

Source and destination IP

Source and destination MAC

Source and destination MAC, source and destination IP

Source and destination MAC, source and destination IP

Destination TCP/UDP port

Destination MAC

Destination MAC, destination IP

Destination MAC, destination IP, destination port

Source TCP/UDP port

Source MAC

Source MAC, source IP

Source MAC, source IP, source port

Source and destination TCP/UDP port

Source and destination MAC

Source and destination MAC, source and destination IP

Source and destination MAC, source and destination IP, source and destination port


Use the option that provides the balance criteria with the greatest variety in your configuration. For example, if the traffic on an EtherChannel is going only to a single MAC address and you use the destination MAC address as the basis of port-channel load balancing, the EtherChannel always chooses the same link in that EtherChannel; using source addresses or IP addresses might result in better load balancing.

Understanding LACP

LACP allows you to configure up to eight interfaces into an EtherChannel.

This section includes the following topics:

LACP Overview

LACP ID Parameters

Port-Channel Modes

LACP Marker Responders

LACP-Enabled and Static EtherChannels Differences

LACP Overview


Note You must enable LACP before the feature functions.


Figure 11-1 shows how individual links can be combined into LACP EtherChannels and channel groups as well as function as individual links.

Figure 11-1 Individual Links Combined into an EtherChannel

With LACP, you can bundle up to eight interfaces in a channel group.


Note When you delete the EtherChannel, Cisco NX-OS automatically deletes the associated channel group. All member interfaces revert to their previous configuration.


You cannot disable LACP while any LACP configurations are present.

LACP ID Parameters

LACP uses the following parameters:

LACP system priority—Each system that runs LACP has an LACP system priority value. You can accept the default value of 32768 for this parameter, or you can configure a value between 1 and 65535. LACP uses the system priority with the MAC address to form the system ID and also uses the system priority during negotiation with other devices. A higher system priority value means a lower priority.


Note The LACP system ID is the combination of the LACP system priority value and the MAC address.


LACP port priority—Each port configured to use LACP has an LACP port priority. You can accept the default value of 32768 for the LACP port priority, or you can configure a value between 1 and 65535. LACP uses the port priority with the port number to form the port identifier. LACP uses the port priority to decide which ports should be put in standby mode when there is a limitation that prevents all compatible ports from aggregating and which ports should be put into active mode. A higher port priority value means a lower priority for LACP. You can configure the port priority so that specified ports have a lower priority for LACP and are most likely to be chosen as active links, rather than hot-standby links.

LACP administrative key—LACP automatically configures an administrative key value equal to the channel-group number on each port configured to use LACP. The administrative key defines the ability of a port to aggregate with other ports. The ability of a port to aggregate with other ports is determined by these factors:

Port physical characteristics, such as the data rate, the duplex capability, and the point-to-point or shared medium state

Configuration restrictions that you establish

Port-Channel Modes

Individual interfaces in EtherChannels are configured with channel modes. When you run static EtherChannels, with no protocol, the channel mode is always set to on. After you enable LACP globally on the device, you enable LACP for each channel by setting the channel mode for each interface to active or passive. You can configure either channel mode for individual links in the LACP channel group.


Note You must enable LACP globally before you can configure an interface in either the active or passive channel mode.


Table 11-2 describes the channel modes.

Table 11-2 Channel Modes for Individual Links in an EtherChannel

Channel Mode
Description

passive

LACP mode that places a port into a passive negotiating state, in which the port responds to LACP packets that it receives but does not initiate LACP negotiation.

active

LACP mode that places a port into an active negotiating state, in which the port initiates negotiations with other ports by sending LACP packets.

on

All static EtherChannels, that is, that are not running LACP, remain in this mode. If you attempt to change the channel mode to active or passive before enabling LACP, the device returns an error message.

You enable LACP on each channel by configuring the interface in that channel for the channel mode as either active or passive. When an LACP attempts to negotiate with an interface in the on state, it does not receive any LACP packets and becomes an individual link with that interface; it does not join the LACP channel group.


Both the passive and active modes allow LACP to negotiate between ports to determine if they can form an EtherChannel, based on criteria such as the port speed and the trunking state. The passive mode is useful when you do not know whether the remote system, or partner, supports LACP.

Ports can form an LACP EtherChannel when they are in different LACP modes as long as the modes are compatible as in the following examples:

A port in active mode can form an EtherChannel successfully with another port that is in active mode.

A port in active mode can form an EtherChannel with another port in passive mode.

A port in passive mode cannot form an EtherChannel with another port that is also in passive mode because neither port will initiate negotiation.

A port in on mode is not running LACP.

LACP Marker Responders

Using EtherChannels, data traffic may be dynamically redistributed due to either a link failure or load balancing. LACP uses the Marker Protocol to ensure that frames are not duplicated or reordered because of this redistribution. Cisco NX-OS supports only Marker Responders.

LACP-Enabled and Static EtherChannels Differences

Table 11-3 provides a brief summary of major differences between EtherChannels with LACP enabled and static EtherChannels.

Table 11-3 EtherChannels with LACP Enabled and Static EtherChannels

Configurations
EtherChannels with LACP Enabled
Static EtherChannels

Protocol applied

Enable globally.

Not applicable.

Channel mode of links

Can be either:

Active

Passive

Can only be On.

Maximum number of links in channel

6

6


Configuring EtherChannels

You can configure multiple EtherChannels on a device.

This section includes the following topics:

Creating an EtherChannel

Adding a Port to an EtherChannel

Configuring Load Balancing Using EtherChannels

Enabling LACP

Configuring Port-Channel Port Modes

Configuring the LACP System Priority and System ID

Configuring the LACP Port Priority

Creating an EtherChannel

You can create an EtherChannel before creating a channel group. Cisco NX-OS automatically creates the associated channel group.


Note If you want LACP-based EtherChannels, you need to enable LACP (see the "Enabling LACP" section).


To create an EtherChannel, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# interface port-channel channel-number

Specifies the port-channel interface to configure, and enters the interface configuration mode. The range is from 1 to 4096. Cisco NX-OS automatically creates the channel group if it does not already exist.

The following example shows how to create an EtherChannel:

switch# configure terminal  
switch(config)# interface port-channel 1  

To remove the EtherChannel and delete the associated channel group, perform this task:

Command
Purpose

switch(config)# no interface port-channel channel-number

Removes the EtherChannel and deletes the associated channel group. See the "Compatibility Requirements" section for details on how the interface configuration changes when you delete the EtherChannel.


Adding a Port to an EtherChannel

You can add a port to a new channel group or to a channel group that already contains ports. Cisco NX-OS creates the EtherChannel associated with this channel group if the EtherChannel does not already exist.


Note If you want LACP-based EtherChannels, you need to enable LACP (see the "Enabling LACP" section).


To configure an EtherChannel, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# interface type slot/port

Specifies the interface that you want to add to a channel group and enters the interface configuration mode.

Step 3 

switch(config-if)# switchport mode trunk

(Optional) Configures the interface as a trunk port.

Step 4 

switch(config-if)# switchport trunk {allowed vlan vlan-id | native vlan vlan-id}

(Optional) Configures necessary parameters for a trunk port.

Step 5 

switch(config-if)# channel-group channel-number

Configures the port in a channel group and sets the mode. The channel-number range is from 1 to 4096. Cisco NX-OS creates the EtherChannel associated with this channel group if the EtherChannel does not already exist1 .

1 This is called implicit EtherChannel creation.

To remove the port from the channel group, perform this task:

Command
Purpose

switch(config)# no channel-group

Removes the port from the channel group. The port reverts to its original configuration.


The following example shows how to add an Ethernet interface 1/4 to channel group 1:

switch# configure terminal  
switch(config)# interface ethernet 1/4  
switch(config-if)# switchport mode trunk  
switch(config-if)# channel-group 1  

Configuring Load Balancing Using EtherChannels

You can configure the load-balancing algorithm for EtherChannels that applies to the entire device.


Note If you want LACP-based EtherChannels, you need to enable LACP (see the "Enabling LACP" section).


To configure load balancing using EtherChannels, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# port-channel load-balance ethernet {destination-ip | destination-mac | destination-port | source-dest-ip | source-dest-mac | source-dest-port | source-ip | source-mac | source-port}

Specifies the load-balancing algorithm for the device. The range depends on the device. The default is source-dest-mac.

Step 3 

switch(config-router)# show port-channel load-balance

(Optional) Displays the port-channel load-balancing algorithm.

The following example shows how to configure source IP load balancing for EtherChannels:

switch# configure terminal  
switch(config)# port-channel load-balance ethernet source-ip  

To restore the default load-balancing algorithm of source-dest-mac for non-IP traffic and source-dest-ip for IP traffic, perform this task:

Command
Purpose

switch(config)# no port-channel load-balance ethernet

Restores the default load-balancing algorithm.


Enabling LACP

LACP is disabled by default; you must enable LACP before you begin LACP configuration. You cannot disable LACP while any LACP configuration is present.

LACP learns the capabilities of LAN port groups dynamically and informs the other LAN ports. Once LACP identifies correctly matched Ethernet links, it facilitates grouping the links into an EtherChannel. The EtherChannel is then added to the spanning tree as a single bridge port.

To enable LACP, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# feature lacp

Enables LACP on the switch.

Step 3 

switch(config)# show system internal clis feature

(Optional) Displays enabled features.

The following example shows how to enable LACP:

switch# configure terminal  
switch(config)# feature lacp  

Configuring Port-Channel Port Modes

After you enable LACP, you can configure the channel mode for each individual link in the LACP EtherChannel as active or passive. This channel configuration mode allows the link to operate with LACP.

When you configure EtherChannels with no associated protocol, all interfaces on both sides of the link remain in the on channel mode.

To configure the LACP link mode, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# interface type slot/port

Specifies the interface to configure, and enters the interface configuration mode.

Step 3 

switch(config-if)# channel-group number mode {active | on | passive}

Specifies the port mode for the link in an EtherChannel. After LACP is enabled, you configure each link or the entire channel as active or passive.

When you run EtherChannels with no associated protocol, the port-channel mode is always on.

The default port-channel mode is on.

switch(config-if)# no channel-group number mode

Returns the port mode to on for the specified interface.

The following example shows how to set the LACP-enabled interface to active port-channel mode for Ethernet interface 1/4 in channel group 5:

switch# configure terminal  
switch(config)# interface ethernet 1/4  
switch(config-if)# channel-group 5 mode active  

Configuring the LACP System Priority and System ID

The LACP system ID is the combination of the LACP system priority value and the MAC address.

To configure the LACP system priority, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# lacp system-priority priority

Configures the system priority for use with LACP. Valid values are 1 through 65535, and higher numbers have lower priority. The default value is 32768.

Step 3 

switch(config-if)# show lacp system-identifier

Displays the LACP system identifier.

The following example shows how to set the LACP system priority to 2500:

switch# configure terminal  
switch(config)# lacp system-priority 2500  

Configuring the LACP Port Priority

When you enable LACP, you can configure each link in the LACP EtherChannel for the port priority.

To configure the LACP link mode and port priority, perform this task:

 
Command
Purpose

Step 1 

switch# configure terminal

Enters configuration mode.

Step 2 

switch(config)# interface type slot/port

Specifies the interface to configure, and enters the interface configuration mode.

Step 3 

switch(config-if)# lacp port-priority priority

Configures the port priority for use with LACP. Valid values are 1 through 65535, and higher numbers have lower priority. The default value is 32768.

The following example shows how to set the LACP port priority for Ethernet interface 1/4 to 40000:

switch# configure terminal  
switch(config)# interface ethernet 1/4  
switch(config-if)# lacp port priority 40000  

Verifying Port-Channel Configuration

To display port-channel configuration information, perform one of the following tasks:

Command
Purpose

switch# show interface port-channel channel-number

Displays the status of a port-channel interface.

switch# show system internal clis feature

Displays enabled features.

switch# show lacp {counters | interface type slot/port | neighbor | port-channel | system-identifier}

Displays LACP information.

switch# show port-channel compatibility-parameters

Displays the parameters that must be the same among the member ports in order to join an EtherChannel.

switch# show port-channel database [interface port-channel channel-number]

Displays the aggregation state for one or more port-channel interfaces.

switch# show port-channel load-balance

Displays the type of load balancing in use for EtherChannels.

switch# show port-channel summary

Displays a summary for the port-channel interfaces.

switch# show port-channel traffic

Displays the traffic statistics for EtherChannels.

switch# show port-channel usage

Displays the range of used and unused channel numbers.

switch# show port-channel database

Displays information on current running of the EtherChannel feature.