Software Configuration Guide, Cisco IOS Release 15.2(2)E (Catalyst 2960, 2960-S, 2960-SF and 2960-Plus Switches)
Configuring EtherChannels
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Configuring EtherChannels

Contents

Configuring EtherChannels

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

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

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.

Figure 1. 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.

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 Switches

You can create an EtherChannel on a switch, on a single switch in the stack, or on multiple switches in the stack (known as 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.

Figure 2. 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. 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 switches and on those switches licensed by vendors to support PAgP. PAgP facilitates the automatic creation of EtherChannels by exchanging PAgP packets between Ethernet ports.

By using PAgP, the switch or switch 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 switch 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 switch port.

PAgP Modes

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

Table 1 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

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 switch 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 switch 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 switch is a physical learner, we recommend that you configure the switch 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 switch 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 switch 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 switches to manage Ethernet channels between switches 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 switch or switch 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 switch port.

LACP Modes

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

Table 2 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 switch 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 switches 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 switch.

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 switch. 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 switch. 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 switch in the network and the kind of traffic that needs to be load-distributed.

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.

Default EtherChannel Configuration

The default EtherChannel configuration is described in this table.

Table 3 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 switch or stack MAC address.

Load-balancing

Load distribution on the switch 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:

  • Do not try to configure more than 24 EtherChannels on the switch.
  • 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 switch or on different switches 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 switch interfaces, remove the EtherChannel configuration from the interfaces before globally enabling IEEE 802.1x on a switch by using the dot1x system-auth-control global configuration command.
  • Do not enable link-state tracking on individual interfaces that will be part of a downstream Etherchannel interface.

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.
  • If you configure an EtherChannel from trunk ports, verify that the trunking mode (ISL or IEEE 802.1Q) is the same on all the trunks. Inconsistent trunk modes on EtherChannel ports can have unexpected results.
  • 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.

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

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 ActionPurpose
    Step 1configure terminal


    Example:
    
    Switch# configure terminal
    
    
     

    Enters the global configuration mode.

     
    Step 2interface interface-id


    Example:
    Switch(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:
    Switch(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:
    Switch(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:
    Switch(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 24.

    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..
    • 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. .
    • 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 switch is connected to a partner that is PAgP-capable, configures the switch 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 6end


    Example:
    Switch(config-if)# end
    
    
     

    Returns to privileged EXEC mode.

     

    Configuring EtherChannel Load-Balancing

    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 ActionPurpose
      Step 1configure terminal


      Example:
      Switch# 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:
      Switch(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 3end


      Example:
      Switch(config)# end
      
      
       

      Returns to privileged EXEC mode.

       

      Configuring EtherChannel Extended Load-Balancing

      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 ActionPurpose
        Step 1configure terminal


        Example:
        Switch# 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:
        Switch(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 3end


        Example:
        Switch(config)# end
        
        
         

        Returns to privileged EXEC mode.

         

        Configuring the PAgP Learn Method and Priority

        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 ActionPurpose
          Step 1configure terminal


          Example:
          Switch# configure terminal
          
          
           

          Enters global configuration mode.

           
          Step 2 interface interface-id


          Example:
          Switch(config)# interface gigabitethernet 1/0/2
          
          
           

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

           
          Step 3 pagp learn-method physical-port


          Example:
          Switch(config-if)# pagp learn-method physical port
          
          
           

          Selects the PAgP learning method.

          By default, aggregation-port learning is selected, which means the switch 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 switch 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:
          Switch(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 5end


          Example:
          Switch(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 switch 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 System Priority

          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 ActionPurpose
            Step 1configure terminal


            Example:
            Switch# configure terminal
            
            
             

            Enters global configuration mode.

             
            Step 2 lacp system-priority priority


            Example:
            Switch(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 3end


            Example:
            Switch(config)# end
            
            
             

            Returns to privileged EXEC mode.

             

            Configuring the LACP Port Priority

            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 ActionPurpose
              Step 1configure terminal


              Example:
              Switch# configure terminal
              
               
               

              Enters global configuration mode.

               
              Step 2 interface interface-id


              Example:
              Switch(config)# interface gigabitethernet 1/0/2
              
              
               

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

               
              Step 3lacp port-priority priority


              Example:
              Switch(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 4end


              Example:
              Switch(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.

              Table 4 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

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

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

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

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

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

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

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

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