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Example: Configuring Link Aggregation 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

Overview and Topology

In this example, the QFX3500 switch has one LAG comprising two 10-Gigabit Ethernet interfaces. This LAG is configured in port mode so that the QFX3500 switch and the VLAN to which it has been assigned can send and receive traffic.

Configuring the Ethernet interfaces as LAGs has the following advantages:

• If one physical port is lost for any reason (a cable is unplugged or a switch port fails), the logical port transparently continues to function over the remaining physical port.
• Link Aggregation Control Protocol (LACP) can optionally be configured for link monitoring and automatic addition and deletion of individual links without user intervention.

Note: If the remote end of the LAG link is a security device, LACP might not be supported because security devices require a deterministic configuration. In this case, do not configure LACP. All links in the LAG are permanently operational unless the switch detects a link failure within the Ethernet physical layer or data link layers.

The topology used in this example consists of one QFX3500 switch with a LAG configured between two of its 10-Gigabit Ethernet interfaces. The QFX3500 switch is connected to an aggregation switch.

Table 1 details the topology used in this configuration example.

Configuration

To configure a LAG between two 10-Gigabit Ethernet interfaces:

CLI Quick Configuration

To quickly configure a LAG between two 10-Gigabit Ethernet interfaces on a QFX3500 switch, copy the following commands and paste them into the QFX3500 switch terminal window:

Step-by-Step Procedure

1. Specify the number of LAGs to be created on the switch:
   [edit chassis]
user@switch# set aggregated-devices ethernet device-count 1
2. Specify the number of links that need to be present for the ae0 LAG interface to be up:
   [edit interfaces]
user@switch# set ae0 aggregated-ether-options minimum-links 1
3. Specify the media speed of the ae0 link:
   [edit interfaces]
user@switch# set ae0 aggregated-ether-options link-speed 10g
4. Assign the LAG to a VLAN:
   [edit interfaces]
user@switch# set ae0 unit 0 family ethernet-switching vlan members vlan200
5. (Optional): Designate one side of the LAG as active for LACP:
   [edit interfaces]
user@switch# set ae0 aggregated-ether-options lacp active
6. (Optional): Designate the interval and speed at which the interfaces send LACP packets:
   [edit interfaces]
user@switch# set ae0 aggregated-ether-options lacp periodic fast

Results

Display the results of the configuration:

Verification

To verify that switching is operational and one LAG has been created, perform these tasks:

• Verifying That LAG ae0.0 Has Been Created
• Verifying That LAG ae0 Has Been Created

Verifying That LAG ae0.0 Has Been Created

Purpose

Verify that LAG ae0.0 has been created on the switch.

Action

show interfaces ae0 terse

Interface               Admin Link Proto    Local                 Remote
ae0                     up    up
ae0.0                   up    up eth-switch

Meaning

The output confirms that the ae0.0 link is up and shows the family and IP address assigned to this link.

Verifying That LAG ae0 Has Been Created

Purpose

Verify that LAG ae0 has been created on the switch

Action

show interfaces ae0 terse

Interface               Admin Link Proto    Local                 Remote
ae0                     up    down
ae0.0                   up    down eth-switch

Meaning

The output shows that the ae0.0 link is down.

Troubleshooting

Troubleshooting a LAG That Is Down

Problem

The show interfaces terse command shows that the LAG is down.

Solution

Check the following:

• Verify that there is no configuration mismatch.
• Verify that all member ports are up.
• Verify that a LAG is part of family ethernet switching (Layer 2 LAG) or family inet (Layer 3 LAG).
• Verify that the LAG member is connected to the correct LAG at the other end.