Link aggregation provides link level redundancy and increases load sharing. Use Link aggregation to bundle the ports into a port group, which is represented as one logical interface to the Media Access Control (MAC) layer.
The switch supports the following types of link aggregation:
MultiLink Trunking (MLT)—a statically configured link bundling method. MLT is not standards based, but it interoperates with static link methods of other vendors.
IEEE 802.3ad based link aggregation, through the Link Aggregation Control Protocol (LACP), dynamically aggregates links as they become available to a trunk group. Link Aggregation Control Protocol dynamically detects whether links can be aggregated into a link aggregation group (LAG) and does so after links become available. Link Aggregation Control Protocol also provides link integrity checking at Layer 2 for all links within the LAG.
Both MLT and IEEE 802.3ad based link aggregation are point-to-point functions.
The switch software offers LACP functionality layered with MLT. This document uses the term MLT with LACP to refer to this functionality.
Split MultiLink Trunking (SMLT) is an option that improves Layer 2 (bridged) resiliency by providing for the addition of failure redundancy with subsecond failover, on top of all standard MLT link failure protection and flexible bandwidth scaling functionality. Use SMLT to connect a device that supports some form of link aggregation, be it a switch or a server, to two distinct separate SMLT endpoints or switches. These SMLT devices form a virtualized Switch Cluster through the SPBM cloud and are referred to as a Virtual Inter-Switch Trunk (vIST) Core Switch pair.
For more information, see the following sections:
You can use LACP on SMLT configurations. The switch provides modifications to the LACP in SMLT configurations. LACP-capable devices can connect to an SMLT aggregation pair.
Note
Virtual IST is not supported on LACP-enabled MLTs.
You can also configure Virtual LACP (VLACP) with an SMLT configuration. VLACP is a modification that provides end-to-end failure detection. VLACP is not a link aggregation protocol.
VLACP implements link status control protocol at the port level. This mechanism periodically checks the end-to-end health of a point-to-point or end-to-end connection. You can run VLACP on single ports or on ports that are part of an MLT.
Note
Do not configure VLACP on LACP-enabled ports. VLACP does not operate properly with LACP.