LAG Overview

The LAG interface could be formed statically or dynamically. LACP protocol helps to bring up the interface dynamically. The two modes of LAG interface are:

LAG interfaces can be used as layer 2 and layer 3 interfaces. A regular layer 2 or layer 3 interface can be created on top of the single LAG interface. These interfaces can be divided based on 802.1q VLAN ID’s. Multiple layer 3 interfaces can be created and each of them can be associated with different instances.

LACP is part of an IEEE specification (802.3ad) that allows several physical ports to be grouped to form a single logical interface. LACP allows a switch to negotiate an LAG by sending LACP packets on its member links. It negotiates the various configuration parameters to bring up the individual member links.

The Interface Holddown feature remains supported when interfaces are grouped in a LAG. For more information about the Interface Holddown feature, see Interface Holddown.

The LAG hashing algorithm distributes traffic across multiple paths or links for load balancing. It achieves this by using various packet header fields (like IP addresses, port numbers, or MAC addresses) to generate a hash value, ensuring probability and an equitable distribution of network traffic.

The following table lists the packet header fields that are used by the LAG hashing algorithm to generate a hash value, which in turn determines how traffic is distributed. A tick (✓) indicates that the field is used by the hashing algorithm. A cross mark (✗) indicates that the field is not used by the hashing algorithm.

Not all features are necessarily supported on each hardware platform. Refer to the Platform Guide for the features and the sub-features that are or are not supported by each platform.

For information on the maximum number of LAG interfaces and members per LAG supported on each hardware platform, refer to the Supported Platforms section of the Platform Guide.