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Example: Configuring Link Aggregation with LACP Between a QFX Series Product and an Aggregation Switch

Requirements

This example uses the following software and hardware components:

• Junos OS Release 11.1 or later for the QFX Series
• One QFX3500 switch

Before you configure LACP, be sure you have:

• Configured the ports on the switches as trunk ports.
• Configured the LAG.

Overview and Topology

The topology in this example is exactly the same as the topology used in the Configuring a LAG Between a QFX Switch and an Aggregation Switch 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).

Configuring LACP for the LAG on the QFX Series

To configure LACP for a QFX Series LAG, 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:

Step-by-Step Procedure

1. Specify the aggregated Ethernet options for the LAG:
   [edit interfaces]
user@switch# set ae0 aggregated-ether-options lacp active periodic fast

Results

Display the results of the configuration:

Verification

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

• Verifying the LACP Settings
• Verifying That the LACP Packets Are Being Exchanged

Verifying the LACP Settings

Purpose

Verify that 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.

Aggregated interface: ae0

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

      xe-0/0/2      Actor    No   Yes    No   No   No   Yes     Fast    Active

      xe-0/0/2    Partner    No   Yes    No   No   No   Yes     Fast   Passive

    LACP protocol:   Receive State    Transmit State           Mux State

      xe-0/0/2          Defaulted     Fast periodic            Detached

 

Meaning

The output indicates that LACP has been set up correctly and is active at one end.

Verifying That the LACP Packets Are Being Exchanged

Purpose

Verify that LACP packets are being exchanged.

Action

Use the show interfaces aex statistics command to display LACP information.

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
      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

Meaning

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

Troubleshooting

To troubleshoot a nonworking LACP link, perform these tasks:

• Troubleshooting a Nonworking LACP Link

Troubleshooting a Nonworking LACP Link

Problem

The LACP link is not working.

Solution

Check the following:

• Remove the 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 (PDUs) are being exchanged by running the monitor traffic-interface lag-member detail command.