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MLAG vs. Stacking vs. LACP

Updated on Jul 29, 2021
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25G Switch

Link aggregation and stacking are common approaches to bundle multiple network connections in one logical link. Compared to conventional connections, these methods are best described as scalable solutions that can provide higher availability, higher reliability and higher bandwidth. MLAG vs. stacking vs. LACP is often asked to define the differences, so this article intends to give an informed explanation of MLAG, LACP, stacking, and the different application scenarios.

Understanding MLAG, LACP, and Stacking

MLAG (Multi-chassis Link Aggregation Group): a non-standard protocol, that implements link aggregation among multiple devices. The devices at both ends of the MLAG send MLAG negotiation packets through the peer-link. The main purpose of MLAG is to deliver system-level redundancy in the event one of the chassis fails.

LACP (Link Aggregation Control Protocol):  a subcomponent of IEEE 802.3ad standard, provides a method to control the bundling of several physical ports together to form a single logical channel. LACP allows a network device to negotiate an automatic bundling of links by sending LACP packets to the peer. For more basics, Understanding Link Aggregation Control Protocol will give you the answer.

Stacking: a technology that enables multiple stacking-capable switches to function as a single logical switch. Stack link is connected by stacking cables to form a stack that connects all the switches in a specific topology. The stacking topology also defines the resiliency of the stacked solution. You can have typically different kinds of cabling options, depending on the switch vendor and models. For more information: Switch Stacking Explained: Basis, Configuration & FAQs.

MLAG vs. Stacking: Which Approach Is Better?

Reliability

  • MLAG: MLAG has higher reliability because its control plane is independent, which isolates the fault domain.

  • Stacking: Stacking has average reliability as its control plane is centralized, which may lead to faults spreading across member devices.

Scalability

  • MLAG: MLAG has strong scalability as it is not limited by the capacity of a single device.

  • Stacking: Stacking has moderate scalability as its control plane capacity is limited by the main device.

Impact on business

  • MLAG: During upgrades, there is minimal interruption to the business. During expansions, the existing network architecture remains unchanged, and there is no impact on existing operations.

  • Stacking: During upgrades, there is an interruption of approximately 20 seconds to 1 minute to the business. During expansions with three or more devices, it is necessary to modify the existing network architecture or restart devices, which affects existing operations.

Network design

  • MLAG: MLAG has a more complex design with a logical dual-node setup.

  • Stacking: Stacking has a simpler design with a logical single-node setup.

Configuration

  • MLAG: MLAG has a more complex configuration with independent configurations for multiple devices.

  • Stacking: Stacking has a simpler design with a logical single-node setup.

In conclusion, stacking has the advantages of simpler configuration and design, but lower flexibility and reliability compared to MLAG. Stacking can add more ports and quickly increase network capacity. Its main advantage is the ease of management. MLAG, although more complex in configuration, offers stronger reliability due to its decoupled control plane and higher network flexibility. Additionally, MLAG also has a stronger impact on business as it can achieve almost no interruption during upgrades or expansions.

The decision to use stacking or MLAG is a matter of weighing up the pros and cons of the option and understanding your network architecture. For more information: MLAG vs. Stacking: What Is Your Option?

MLAG vs. LACP: Similarities and Differences

Similarities

MLAG and LACP are very similar and accomplish the same goal. They are link aggregation methods of aggregating multiple network connections in parallel to increase throughput and provide redundancy in case one of the links fails.

Differences

  • LACP provides enhanced functionality for link aggregation groups (LAGs) by automating configuration and maintenance. LACP-enabled ports automatically form trunk groups without manual configuration. When a member link stops sending LACPDUs, it is removed from the LAG to minimize packet loss. If both devices support LACP, it is recommended over static LAG, but LAG configuration is still required on each device.

  • LACP can be implemented between multi-vendor switches.

  • The implementation of MLAG varies by vendor, all of which are proprietary.

Stacking vs. LACP: What Is the Difference?

  • LACP cannot bundle links across multiple switches. It can only bundle links within a single ethernet switch for increased bandwidth and redundancy. The primary purpose is to improve link-level reliability. To establish an aggregated connection between switches A, B, and C, you must enable LACP on specific ports on each switch and make physical connections.

  • Stacking technology allows for bundling multiple switches to act as a single logical switch, to increase equipment-level reliability. Those switches are directly connected by stacking cable for stack link.

FAQ

Can I Use LACP ports to create the flexible switch stack? Can I configure stacking and LACP at the same time?

Stacking ports don't use LACP, they use their own stacking protocol. You need two ports on each switch to be configured for stacking. The ports between the switches should be configured as a ring to send packets. Once the switches are stacked, you can use LACP across the switches in the stack to other things.

Is it necessary to configure the LACP function after the switches are stacked?

That depends on the customer's need. If customers want to increase the link reliability and bandwidth of the downlink, they can use the LACP link aggregation; if the customer is only for the convenience of management, then they do not configure.

Can the MLAG function be used for stacking? Is MLAG an Alternative to Stackable Switches?

It's ok. MLAG can expand port capacity beyond the limitation of switch stacking - simply adding another switch East or West by creating another MLAG to another switch. Using MLAG, each switch is independently able for forwarding traffic without passing to a master switch. The number of switches can be stacked is limited, and the added switch needs to not only be from the same vendor as the other members of the stack but the same model, software version, and license pack as well.

A switch supports stacking but does not support MLAG. Which scenario is applicable?

When the port density of a system is insufficient for an increased number of users, you can add new member switches to the stack to increase ports. The configuration and design of stacking is simpler. Virtualizing two devices into a logical device can achieve functions similar to MLAG. The downstream device is connected to two switches separately, and LACP is configured, which can achieve the effect of redundancy, and there will be no loops.

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