About Link Aggregation

A link aggregation (LA) interface is a group of physical interfaces that you configure to work together as a single logical interface. You can use a link aggregation interface to increase the cumulative throughput beyond the capacity of a single physical interface, and to provide redundancy if there is a physical link failure. When you use link aggregation, you connect the link aggregation interfaces to a switch, and configure the connected switch to use the same link aggregation mode and link speed.

You can configure a link aggregation interface only on an XTM device configured in mixed routing mode. A link aggregation interface can be configured as an External, Trusted, Optional, or Custom interface, or as a member of a VLAN or Bridge interface. You can use a link aggregation interface in most of the same ways that you use a physical interface. For example, you can use it in the configuration of policies, multi-WAN, VPN, DHCP, and PPPoE.

Requirements and Limitations

Link Aggregation Modes

On a supported Fireware XTM device with Fireware XTM Pro, you can configure a link aggregation interface in one of three modes. For all modes, a member interface can be active only when the member interface link status is up. Whether a member interface is active depends on both the link status of the physical interface and the link aggregation mode.

Dynamic (802.3ad)

All physical interfaces that are members of the link aggregation interface can be active. The physical interface used for traffic between any source and destination is selected based on Link Aggregation Control Protocol (LACP), as described in the IEEE 802.3ad dynamic link aggregation specification.

Static

All physical interfaces that are members of the link aggregation interface can be active. The same physical interface is always used for traffic between a given source and destination based on source/destination MAC address and source/destination IP address. This mode provides load balancing and fault tolerance.

Active-backup

In this mode, at most only one member interface in the link aggregation group is active at a time. The other member interfaces in the link aggregation group become active only if the active interface fails. This mode provides fault tolerance for connections to network switches that do not support link aggregation.

To use dynamic or static link aggregation, you must also configure link aggregation on the connected switch. To use Active-backup mode it is not necessary to enable link aggregation on your switches.

See Also

Configure Link Aggregation

Common Interface Settings

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