Introduction

A Link Aggregation Group (LAG) is a method of combining multiple physical network connections into a single logical connection. This technique, also known as link bundling or port trunking, is widely used in computer networking to increase bandwidth, improve reliability, and provide redundancy.

Key Features and Characteristics

• Increased Bandwidth: LAGs combine the capacity of multiple links, effectively multiplying the available bandwidth.
• Improved Reliability: If one link fails, traffic can be automatically redirected to the remaining active links.
• Load Balancing: Traffic can be distributed across multiple links for optimal performance.
• Redundancy: LAGs provide fault tolerance by maintaining connectivity even if individual links fail.
• Standardization: LAGs are defined in IEEE 802.1AX (formerly 802.3ad) standard.
• Constraints: LAGs cannot span multiple AWS Direct Connect locations or Regions.

Modifications to LAGs

Understanding which modifications can be made to an existing LAG and which require creating a new LAG is crucial for network administrators. Let's explore these in detail:

Modifications That Can Be Done to an Existing LAG

1. Adding or Removing Ports:
   • Most LAG implementations allow adding new ports to an existing LAG without disruption.
   • Removing ports is typically possible as long as at least one port remains in the LAG.
2. Changing Load Balancing Algorithm:
   • The algorithm determining how traffic is distributed across LAG members can often be modified without recreating the LAG.
3. Adjusting LACP (Link Aggregation Control Protocol) Settings:
   • Changing LACP modes (active/passive) or timers can usually be done on-the-fly.
4. Modifying LAG Description or Name:
   • Updating the LAG's descriptive information doesn't typically require recreation.
5. Changing QoS (Quality of Service) Settings:
   • QoS policies applied to the LAG can often be modified without disruption.
6. Adjusting Flow Control Settings:
   • Enabling or disabling flow control on the LAG can typically be done without recreation.

Modifications Requiring Creation of a New LAG