Chapter 3: Link Aggregation Fundamentals; Link Aggregation Overview - Avaya 8600 Configuration Manual

Chapter 3: Link aggregation fundamentals

This chapter describes link aggregation concepts and the features supported on the Avaya Ethernet
Routing Switch 8800/8600.

Link aggregation overview

Link aggregation provides link level redundancy and increases load sharing. Link aggregation
allows you to bundle the ports into a port group, which is represented as one logical interface
to the MAC layer.
The Avaya Ethernet Routing Switch 8800/8600 supports the following types of link
aggregation:
• MultiLink Trunking (MLT)—a statically configured link bundling method. MLT is not
standards based, but will interoperate with other vendors' static link methods.
• IEEE 802.3ad-based link aggregation, through the Link Aggregation Control Protocol
(LACP), supports a dynamic link aggregation function as they become available to a trunk
group. LACP dynamically detects whether links can be aggregated into a link aggregation
group (LAG) and does so when links become available. LACP also provides link integrity
checking at Layer 2 for all links within the LAG.
Both MLT and IEEE 802.3ad-based link aggregation are defined as point-to-point functions.
The Avaya Ethernet Routing Switch 8800/8600 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 switch failure redundancy with sub-second failover, on top of all
standard MLT link failure protection and flexible bandwidth scaling functionality. SMLT allows
you to connect any device which supports some form of link aggregation, be it a switch or a
server, to two distinct separate SMLT endpoints or switches. These SMLT switches form a
Switch Cluster and are referred to as an IST Core Switch pair.
LACP can also be used on SMLT configurations. The Avaya Ethernet Routing Switch
8800/8600 provides modifications to LACP in SMLT configurations. This allows LACP-capable
devices to connect to an SMLT aggregation pair. Avaya recommends that LACP not be
configured on the IST MLT.
Virtual LACP (VLACP) is an Avaya 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. It is a mechanism to periodically check 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 a
MLT. Avaya recommends that you do not configure VLACP on LACP-enabled ports. VLACP
Configuration — Link Aggregation, MLT, and SMLT January 2012 11