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Configuring Link Aggregation

 

Use the link aggregation feature to aggregate one or more links to form a virtual link or aggregation group. The MAC client can treat this virtual link as if it were a single link. Link aggregation increases bandwidth, provides graceful degradation as failure occurs, and increases link availability.

Note

An interface with an already configured IP address cannot form part of the aggregation group.

Note

On QFX5100, QFX5200, EX4600, QFX10002 , and QFX10008 standalone switches and on QFX5100 Virtual Chassis and EX4600 Virtual Chassis, you can configure a mixed rate of link speeds for the aggregated Ethernet bundle. Load balancing will not work if you configure link speeds that are not supported. (Platform support depends on the Junos OS release in your installation.)

Creating an Aggregated Ethernet Interface

To create an aggregated Ethernet interface:

  1. Specify the number of aggregated Ethernet interfaces to be created:
    [edit chassis]

    user@switch# set aggregated-devices interfaces device-count device-count

    For example, to specify 5:

    [edit chassis]

    user@switch# set aggregated-devices interfaces device-count 5
  2. Specify the minimum number of links for the aggregated Ethernet interface (aex), that is, the defined bundle, to be labeled “up”:Note

    By default only one link must be up for the bundle to be labeled “up”.

    [edit interfaces]

    user@switch# set interface-name aggregated-ether-options minimum-links minimum-links

    For example, to specify 5:

    [edit interfaces]

    user@switch# set interface-name aggregated-ether-options minimum-links 5
  3. Specify the link speed for the aggregated Ethernet bundle:
    [edit interfaces]

    user@switch# set interface-name aggregated-ether-options link-speed link-speed

    For example, to specify 10g:

    [edit interfaces]

    user@switch# set interface-name aggregated-ether-options link-speed 10g
  4. Specify the members to be included within the aggregated Ethernet bundle:
    [edit interfaces]

    user@switch# set interface-name ether-options 802.3ad aex

    user@switch# set interface-name ether-options 802.3ad aex

Configuring the VLAN Name and VLAN ID Number

Note

VLANs are not supported on OCX Series switches.

[edit vlans]

user@switch# set vlan-name vlan-id vlan-id-number

For example, 100.

Note

When you add or remove a vlan from a LAG interface, the interface goes down and comes back (flaps). The flapping happens when a low speed SFP is plugged into a relatively high speed port. To avoid flapping, configure the port speed to match the speed of the SFP.

Configuring Aggregated Ethernet LACP (CLI Procedure)

For aggregated Ethernet interfaces on EX Series switches, you can configure the Link Aggregation Control Protocol (LACP). LACP is one method of bundling several physical interfaces to form one logical interface. You can configure aggregated Ethernet interfaces with or without LACP enabled.

LACP was designed to achieve the following:

  • Automatic addition and deletion of individual links to the bundle without user intervention

  • Link monitoring to check whether both ends of the bundle are connected to the correct group

Note

You can also configure LACP link protection on aggregated Ethernet interfaces. For information, see Configuring LACP Link Protection of Aggregated Ethernet Interfaces for Switches.

The Junos OS implementation of LACP provides link monitoring but not automatic addition and deletion of links.

Before you configure LACP for EX Series, be sure you have:

When LACP is enabled, the local and remote sides of the aggregated Ethernet links exchange protocol data units (PDUs), which contain information about the state of the link. You can configure Ethernet links to actively transmit PDUs, or you can configure the links to passively transmit them (sending out LACP PDUs only when they receive them from another link). One side of the link must be configured as active for the link to be up.

Note

Do not add LACP to a LAG if the remote end of the LAG link is a security device, unless the security device supports LACP. Security devices often do not support LACP because they require a deterministic configuration.

To configure LACP:

  1. Enable the LACP mode:
    [edit interfaces]

    user@switch# set aex aggregated-ether-options lacp mode

    For example, to specify the mode as active, execute the following command:

    [edit interfaces]

    user@switch# set aex aggregated-ether-options lacp active
    Note

    LACP decides active and back up state of links. When configuring LACP, state of the backup link should not be configured manually as down. The following command is not supported if LACP is configured:set interfaces ae0 aggregated-ether-options link-protection backup-state down

  2. Specify the interval and speed at which the interfaces send LACP packets:
    [edit interfaces]

    user@switch# set aex aggregated-ether-options lacp periodic interval

    For example, to specify the interval as fast, execute the following command:

    [edit interfaces]

    user@switch# set aex aggregated-ether-options lacp periodic fast
Note

The LACP process exists in the system only if you configure the system in either active or passive LACP mode.