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Configuring Link Aggregation Control Protocol

 

Link Aggregation Control Protocol (LACP) provides a standard means for information exchange between the systems on a link. The below topics discuss the overview of LACP on standalone devices, examples of configuring LACP, LAG and LACP support line devices.

Understanding LACP on Standalone Devices

Link Aggregation Control Protocol (LACP) provides a standardized means for exchanging information between partner systems on a link. Within LACP, the local end of a child link is known as the actor and the remote end of the link is known as the partner.

LACP is enabled on an aggregated Ethernet interface by setting the mode to either passive or active. However, to initiate the transmission of link aggregation control protocol data units (PDUs) and response link aggregation control PDUs, you must enable LACP at both the local and remote ends of the links, and one end must be active:

  • Active mode—If either the actor or partner is active, they exchange link aggregation control PDUs. The actor sends link aggregation control PDUs to its protocol partner that convey what the actor knows about its own state and that of the partner’s state.

  • Passive mode—If the actor and partner are both in passive mode, they do not exchange link aggregation control PDUs. As a result, the aggregated Ethernet links do not come up. In passive transmission mode, links send out link aggregation control PDUs only when they receive them from the remote end of the same link.

By default, the actor and partner transmit link aggregation control PDUs every second. You can configure different periodic rates on active and passive interfaces. When you configure the active and passive interfaces at different rates, the transmitter honors the receiver’s rate.

You configure the interval at which the interfaces on the remote side of the link transmit link aggregation control PDUs by configuring the periodic statement on the interfaces on the local side. It is the configuration on the local side that specifies the behavior of the remote side. That is, the remote side transmits link aggregation control PDUs at the specified interval. The interval can be fast (every second) or slow (every 30 seconds).

Note

Starting with Junos OS Release 15.1X49-D40, LACP is supported in Layer 2 transparent mode in addition to existing support in Layer 3 mode.

This example shows how to configure LACP.

Requirements

This example uses an SRX Series device.

Before you begin:

  • Determine which interfaces to use and verify that they are in switch mode. See Understanding VLANs.

Overview

In this example, for aggregated Ethernet interfaces, you configure the Link Aggregation Control Protocol (LACP). LACP is one method of bundling several physical interfaces to form one logical interface.

Configuration

CLI Quick Configuration

To quickly configure this section of the example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure LACP:

  1. Configure the interfaces for ae0.
  2. Configure ae0 interface for vlan tagging.
  3. Configure LACP for ae0 and configure periodic transmission of LACP packets.
  4. Configure ae0 as a trunk port.
  5. Configure the VLAN.
  6. Add the ae0 interface to the VLAN.
  7. If you are done configuring the device, commit the configuration.

Results

From configuration mode, confirm your configuration by entering the show interfaces command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verification

Verifying LACP Statistics

Purpose

Display LACP statistics for aggregated Ethernet interfaces.

Action

From operational mode, enter the show lacp statistics interfaces ae0 command.

user@host> show lacp statistics interfaces ae0

Meaning

The output shows LACP statistics for each physical interface associated with the aggregated Ethernet interface, such as the following:

  • The LACP received counter that increments for each normal hello packet received

  • The number of LACP transmit packet errors logged

  • The number of unrecognized packet errors logged

  • The number of invalid packets received

Use the following command to clear the statistics and see only new changes:

Verifying LACP Aggregated Ethernet Interfaces

Purpose

Display LACP status information for aggregated Ethernet interfaces.

Action

From operational mode, enter the show lacp interfaces ae0 command.

user@host> show lacp interfaces ae0

Meaning

The output shows aggregated Ethernet interface information, including the following information:

  • The LACP state—Indicates whether the link in the bundle is an actor (local or near-end of the link) or a partner (remote or far-end of the link).

  • The LACP mode—Indicates whether both ends of the aggregated Ethernet interface are enabled (active or passive)—at least one end of the bundle must be active.

  • The periodic link aggregation control PDU transmit rate.

  • The LACP protocol state—Indicates the link is up if it is collecting and distributing packets.

Verifying LACP on Standalone Devices

Verifying LACP Statistics

Purpose

Display LACP statistics for aggregated Ethernet interfaces.

Action

From operational mode, enter the show lacp statistics interfaces ae0 command.

user@host> show lacp statistics interfaces ae0

The output shows LACP statistics for each physical interface associated with the aggregated Ethernet interface, such as the following:

  • The LACP received counter that increments for each normal hello

  • The number of LACP transmit packet errors logged

  • The number of unrecognized packet errors logged

  • The number of invalid packets received

Use the following command to clear the statistics and see only new changes:

Verifying LACP Aggregated Ethernet Interfaces

Purpose

Display LACP status information for aggregated Ethernet interfaces.

Action

From operational mode, enter the show lacp interfaces ae0 command.

user@host> show lacp interfaces ae0

The output shows aggregated Ethernet interface information, including the following information:

  • The LACP state—Indicates whether the link in the bundle is an actor (local or near-end of the link) or a partner (remote or far-end of the link).

  • The LACP mode—Indicates whether both ends of the aggregated Ethernet interface are enabled (active or passive)—at least one end of the bundle must be active.

  • The periodic link aggregation control PDU transmit rate.

  • The LACP protocol state—Indicates the link is up ifit is collecting and distributing packets.

LAG and LACP Support Line Devices with I/O Cards (IOCs)

Note

The following notes apply to 'LAG and LACP Support on SRX5000 Line Devices' as outlined in this document.

  • Cross-IOC LAG interfaces do not support Layer 2 transparent mode.

  • Mixed interface speeds are supported on the same aggregated bundle.

  • A redundant Ethernet interface or aggregated Ethernet interface must contain child interfaces from the same IOC type. For example, if one child link is from 10-Gigabit Ethernet on IOC2, the second child link should also be from IOC2. Similarly, both child interfaces can be from IOC3. Configuring child interfaces by mixing links from both IOC2 and IOC3 is not supported.

LAG and LACP Support on the SRX5000 Module Port Concentrator

The SRX5000 Module Port Concentrator (SRX5K-MPC) on SRX5400, SRX5600, and SRX5800 devices supports link aggregation groups (LAGs) and Link Aggregation Control Protocol (LACP).

Support for LAGs based on IEEE 802.3ad makes it possible to aggregate physical interface links on your device. LAGs provide increased interface bandwidth and link availability by linking physical ports and load-balancing traffic crossing the combined interface.

LACP provides a standardized means for exchanging information between partner (remote or far-end of the link) systems on a link. This exchange allows their link aggregation control instances to reach agreement on the identity of the LAG to which the link belongs, and then to move the link to that LAG. This exchange also enables the transmission and reception processes for the link to function in an orderly manner.

The following LAG and LACP features are supported on the SRX5K-MPC:

  • Bandwidth aggregation—Increases bandwidth, provides graceful degradation as failure occurs, and increases availability.

  • Link redundancy and load balancing (within chassis cluster)—Provides network redundancy by load-balancing traffic across all available links. If one of the links should fail, the system automatically load-balances traffic across all remaining links.

  • Dynamic link management—Enables automatic addition and deletion of individual links to the aggregate bundle without user intervention.

LACP supports the following features:

  • LACP bundles several physical interfaces to form one logical interface by exchanging LACP packets between the local interface and the remote interface. LACP monitors the link for changes in interface state by exchanging a periodic LACP heartbeat between two sides. Any changes in interface state are reflected in the LACP packet.

  • Normally after an LACP is configured and committed, two sides start to exchange interface and port information. Once they identify each other and match the LACP state machine criteria, the LACP is declared as up. You can deactivate or delete the LACP configuration.

  • By default, the LACP packets are exchanged in every second. You can configure the LACP interval as fast (every second) or slow (every 30 seconds) to ensure the health of the interfaces.

  • LACP supports distributed and centralized modes. Chassis cluster setup is recommended to operate with LACP distributed mode, which handles chassis cluster failover better. The centralized mode might experience traffic loss during failover.

SRX5K-MPCs on SRX5000 line devices provide active and standby support with redundant Ethernet interface LAGs in chassis cluster deployments.

LAG and LACP Support on the SRX5000 Line IOCs in Express Path Mode

Starting in Junos OS Release 15.1X49-D40, the IOC2 and IOC3 cards on SRX5400, SRX5600, and SRX5800 devices support link aggregation groups (LAGs) and Link Aggregation Control Protocol (LACP) in Express Path mode.

You can use the links in a LAG as ingress or egress interfaces in Express Path mode. The LAG links can include links from cards such as IOC2 or IOC3. For a LAG link to qualify for Express Path, all its member links should be connected to Express Path-enabled network processors. If Express Path is disabled on any of the member links in a LAG, a regular session (non-Express Path session) is created.

Example: Configuring LAG Interface on an Line Device with IOC2 or IOC3

Starting in Junos OS Release 15.15X49-D40, IEEE 802.3ad link aggregation enables you to group Ethernet interfaces to form a single, aggregated Ethernet interface. This single, aggregated Ethernet interface is also known as a LAG or bundle. The LACP provides additional functionality for LAGs.

This example shows how to configure LAG on an SRX Series device using the links from either IOC2 or IOC3 in Express Path mode.

Requirements

This example uses the following software and hardware components:

  • Junos OS Release 15.1X49-D40 or later for SRX Series devices.

  • SRX5800 with IOC2 or IOC3 with Express Path enabled on IOC2 and IOC3. For details, see Express Path.

Overview

In this example, you create a logical aggregated Ethernet interface and define the parameters associated with the logical aggregated Ethernet interface, such as a logical unit, interface properties, and LACP. Next, define the member links to be contained within the aggregated Ethernet interface—for example, four 10-Gigabit Ethernet interfaces. Finally, configure an LACP for link detection.

The following member links are used in this example:

  • xe-0/0/8

  • xe-0/0/9

  • xe-1/0/8

  • xe-1/0/9

  • xe-3/1/4

  • xe-3/1/5

  • xe-5/1/4

  • xe-5/1/5

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, delete, and then copy and paste the commands into the CLI at the [edit] hierarchy level, and then enter commit from configuration mode.

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For instructions on how to do that, see the Junos OS CLI User Guide.

To configure LAG Interfaces:

  1. Specify the number of aggregated Ethernet interfaces to be created.
  2. Specify the members to be included within the aggregated Ethernet bundle.
  3. Assign an IP address to ae0 and ae1.
  4. Set the LACP on reth0.

Results

From configuration mode, confirm your configuration by entering the show interfaces command. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Verification

Verifying LACP on Redundant Ethernet Interfaces

Purpose

Display LACP status information for redundant Ethernet interfaces.

Action

From operational mode, enter the show lacp interfaces command to check that LACP has been enabled as active on one end.

user@host> show lacp interfaces

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

Release History Table
Release
Description
Starting in Junos OS Release 15.1X49-D40, the IOC2 and IOC3 cards on SRX5400, SRX5600, and SRX5800 devices support link aggregation groups (LAGs) and Link Aggregation Control Protocol (LACP) in Express Path mode.
Starting in Junos OS Release 15.15X49-D40, IEEE 802.3ad link aggregation enables you to group Ethernet interfaces to form a single, aggregated Ethernet interface.