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Example: Configuring Aggregated Ethernet High-Speed Uplinks with LACP Between an EX4200 Virtual Chassis Access Switch and an EX4200 Virtual Chassis Distribution Switch

 

EX Series switches allow you to combine multiple 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 an EX4200 Virtual Chassis Access Switch and an EX4200 Virtual Chassis Distribution Switch:

Requirements

This example uses the following software and hardware components:

  • Junos OS Release 9.0 or later for EX Series switches

  • Two EX4200-48P switches

  • Two EX4200-24F switches

  • Four EX Series XFP uplink modules

Before you configure LACP, be sure you have:

Overview and Topology

This example assumes that you are familiar with Example: Configuring Aggregated Ethernet High-Speed Uplinks Between an EX4200 Virtual Chassis Access Switch and an EX4200 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.

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

Configuring LACP for the LAGs on the Virtual Chassis Access Switch

To configure LACP for the access switch LAGs, 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:

[edit]

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

Results

Display the results of the configuration:

Configuring LACP for the LAGs on the Virtual Chassis Distribution Switch

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 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

Results

Display the results of the configuration:

Verification

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

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.

user@Host-A> show lacp interfaces xe-0/1/0

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.

user@Host-A> show interfaces ae0 statistics

Meaning

The output here shows that the link is down and that no protocol data units (PDUs) are being exchanged.

Troubleshooting

To troubleshoot a nonworking LACP link, perform these tasks:

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.