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Example: Configuring Aggregated Ethernet High-Speed Uplinks with LACP Between a Virtual Chassis Access Switch and a Virtual Chassis Distribution Switch

EX-series switches allow you to combine one to eight Ethernet links into one logical interface for higher bandwidth and redundancy. The ports that are combined in this manner are referred to as a link aggregation group (LAG) or bundle. EX-series switches allow you to further enhance these links by configuring Link Aggregation Control Protocol (LACP).

This example describes how to overlay LACP on the LAG configurations that were created in Example: Configuring Aggregated Ethernet High-Speed Uplinks Between a Virtual Chassis Access Switch and a Virtual Chassis Distribution Switch:

Requirements

This example uses the following software and hardware components:

  • JUNOS for EX-series Release 9.0 or later
  • Two EX-series 4200-48P switches
  • Two EX-series 4200-24F switches
  • Four EX-series EX-UM-2XFP uplink modules

Before you configure LACP, be sure you have:

Overview and Topology

This example assumes that you are already familiar with the Example: Configuring Aggregated Ethernet High-Speed Uplinks between Virtual Chassis Access Switch and Virtual Chassis Distribution Switch. The topology in this example is exactly the same as the topology in that other example. This example shows how to use LACP to enhance the LAG functionality.

LACP exchanges are made between actors (the transmitting link) and partners (the receiving link). The LACP mode can be either active or passive.

Note: If the actor and partner are both in passive mode, they do not exchange LACP packets, which results in the aggregated Ethernet links not coming up. By default, LACP is in passive mode. To initiate transmission of LACP packets and responses to LACP packets, you must enable LACP in active mode.

By default, the actor and partner send LACP packets every second. You can configure the interval at which the interfaces send LACP packets by including the periodic statement at the [edit interfaces interface-name aggregated-ether-options lacp] hierarchy level.

The interval can be fast (every second) or slow (every 30 seconds).

Configuration

To configure LACP for the two uplink LAGs from the virtual chassis access switch to the virtual chassis distribution switch, perform these tasks:

CLI Quick Configuration

To quickly configure LACP for the access switch LAGs, copy the following commands and paste them into the switch terminal window:


set interfaces ae0 aggregated-ether-options lacp active periodic fast

set interfaces ae1 aggregated-ether-options lacp active periodic fast

Step-by-Step Procedure

To configure LACP for Host-A LAGs ae0 and ae1:

  1. Specify the aggregated Ethernet options for both bundles:
    [edit interfaces]
    user@Host-A#set ae0 aggregated-ether-options lacp active periodic fast
    user@Host-A#set ae1 aggregated-ether-options lacp active periodic fast

Configuration Results

Display the results of the configuration:

CLI Quick Configuration

To quickly configure LACP for the distribution switch LAGs, copy the following commands and paste them into the switch terminal window:


[edit interfaces]
set ae0 aggregated-ether-options lacp passive periodic fast
set ae1 aggregated-ether-options lacp passive periodic fast

Step-by-Step Procedure

To configure LACP for Host D LAGs ae0 and ae1:

  1. Specify the aggregated ethernet options for both bundles:
    [edit interfaces]
    user@Host-D#set ae0 aggregated-ether-options lacp passive periodic fast
    user@Host-D#set ae1 aggregated-ether-options lacp passive periodic fast

Step-by-Step Procedure

    Configuration Results

    Display the results of the configuration:

    Verification

    To verify that LACP packets are being exchanged, perform these tasks:

    Verifying the LACP Settings

    Purpose

    To verify that the LACP has been set up correctly.

    Action

    Use the show lacp interfaces interface-name command to check that LACP has been enabled as active on one end.


    show lacp interfaces xe-0/1/0 
    show lacp interfaces xe-0/1/0

Aggregated interface: ae0

    LACP state:       Role   Exp   Def  Dist  Col  Syn  Aggr  Timeout  Activity

      xe-0/1/0      Actor    No   Yes    No   No   No   Yes     Fast    Active

      xe-0/1/0    Partner    No   Yes    No   No   No   Yes     Fast   Passive

    LACP protocol:   Receive State    Transmit State           Mux State

      xe-0/1/0          Defaulted     Fast periodic            Detached

    Verifying That the LACP Packets are Being Exchanged

    Purpose

    To verify that LACP packets are being exchanged.

    Action

    Use the show interfaces lag-namestatisticscommand to display LACP information.


    show interfaces ae0 statistics 
    Physical interface: ae0, Enabled, Physical link is Down
  Interface index: 153, SNMP ifIndex: 30
  Link-level type: Ethernet, MTU: 1514, Speed: Unspecified, Loopback: Disabled,
  Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1,
  Minimum bandwidth needed: 0
  Device flags   : Present Running
  Interface flags: Hardware-Down SNMP-Traps Internal: 0x0
  Current address: 02:19:e2:50:45:e0, Hardware address: 02:19:e2:50:45:e0
  Last flapped   : Never
  Statistics last cleared: Never
    Input packets : 0
    Output packets: 0
  Input errors: 0, Output errors: 0

  Logical interface ae0.0 (Index 71) (SNMP ifIndex 34)
    Flags: Hardware-Down Device-Down SNMP-Traps Encapsulation: ENET2
    Statistics        Packets        pps         Bytes          bps
    Bundle:
        Input :             0          0             0            0
        Output:             0          0             0            0
    Protocol inet, MTU: 1500
      Flags: None
      Addresses, Flags: Dest-route-down Is-Preferred Is-Primary
        Destination: 10.10.10/24, Local: 10.10.10.1, Broadcast: 10.10.10.255

    What it Means

    The output here shows that the link is down and that no PDUs are being exchanged.

    Troubleshooting

    These are some tips for troubleshooting:

    Problem

    LACP link is not working.

    Solution

    Check the following:

    • Remove LACP configuration and verify whether the static lag is up.
    • Verify that LACP is configured at both ends.
    • Verify that LACP is not passive at both ends.
    • Verify whether LACP protocol data units are being exchanged by running the monitor traffic-interface lag-member detail command.