LAG/LACP

What Is LAG and How Does It Work?

Link aggregation combines multiple Ethernet links into a single logical connection to boost bandwidth and performance. Commonly used in switches, servers, and NAS, it supports high throughput and fault tolerance. By evenly distributing traffic and providing redundancy, link aggregation ensures uninterrupted connections even if a single link fails. Adhering to IEEE standards like 802.3ad and 802.1AX, it offers a cost-effective way to enhance network reliability and efficiency.

A Link Aggregation Group (LAG) is an implementation of link aggregation technology, combining multiple ports between two switches into a single logical connection. This setup effectively increases bandwidth by utilizing parallel links.

LAG also enhances network reliability through link redundancy and traffic load balancing. If one link fails, the remaining links automatically handle traffic, ensuring uninterrupted data transmission and preventing packet loss.

Link Aggregation Groups (LAGs) come in two primary types: static (manual) and dynamic.

Static LAGs require manual configuration by administrators, who create Eth-Trunk interfaces and assign member interfaces to them. This method operates without a negotiation protocol, relying entirely on manual setup.

Dynamic LAGs, on the other hand, are configured automatically using the Link Aggregation Control Protocol (LACP). LACP allows devices to negotiate link bundling and establish a LAG efficiently. It also enhances reliability by detecting link failures and swiftly redirecting traffic to other active links within the group.

It’s important to note that not all devices support dynamic LAGs with LACP—some only allow static LAGs. To ensure compatibility, consult the device's user manual or specifications before making a purchase.

What Is LACP and How Does It Work?

LACP (Link Aggregation Control Protocol), a key component of the IEEE 802.3ad standard, provides an efficient way to bundle multiple physical links between network devices into a single logical connection. This approach enhances network bandwidth and reliability without requiring changes to the existing infrastructure.

In LACP mode, even if one link fails, other links within the LACP group seamlessly take over, ensuring load balancing and uninterrupted data transmission. When two switches enable LACP, they exchange LACP Data Units (LACPDUs) to communicate and establish their system priorities.

During negotiation, the switch with the higher priority is designated as the Actor, while the one with lower priority becomes the Partner. If both switches have the same priority, the one with the smaller MAC address assumes the Actor role. Afterward, the switches select active ports based on the Actor port’s priority. If priorities are identical, the port with the lower number is chosen.

Once active ports are determined, the two switches form a port channel (LACP group). All active links in the group then work together to distribute traffic efficiently and maintain smooth, stable network communication. This dynamic coordination ensures both high performance and fault tolerance in the network.

What Is the Difference Between LAG and LACP？

LAG (Link Aggregation Group) is a fundamental technology for bundling links and balancing network traffic, often referred to as manual mode because it requires user configuration. In this mode, users manually create a port channel and add the desired member interfaces to it. Once established, all member links actively participate in data forwarding. If one link fails, the remaining active links automatically redistribute the traffic, maintaining load balancing. However, manual LAG has limitations—it can only detect link disconnections and is unable to identify deeper issues like link layer failures or connection errors.

In comparison, LACP (Link Aggregation Control Protocol) is an advanced protocol that automates the configuration and maintenance of LAG. LACP automatically creates port channels and uses a standardized negotiation mechanism to enable switches to dynamically form and manage aggregated links based on their configurations. After the link is established, LACP continuously monitors and maintains its status.

When link conditions change, LACP can quickly adjust the aggregation group by adding or removing links as needed. If an active link fails, LACP automatically selects a backup link to ensure that data forwarding remains uninterrupted. Unlike manual LAG, LACP can detect not only link disconnections but also more subtle issues such as link layer errors or connection mismatches.

LACP offers significant advantages over static LAG. It ensures higher network reliability by promptly detecting and resolving link failures, maintaining stable port status, and minimizing packet loss. It also facilitates automatic configuration verification between devices, reducing the risk of wiring or setup errors. Even in setups involving media converters, LACP ensures seamless traffic management and robust network performance, making it an essential tool for modern network environments.