Introduction:

Link aggregation is a technique used to bundle multiple physical links between network devices into a single logical link, increasing bandwidth, improving redundancy, and providing load balancing. There are several modes available for establishing link aggregation, depending on the protocol being used (LACP or PAGP) and the level of control required. This article will discuss the different modes for establishing link aggregation and their respective advantages and disadvantages.

LACP Modes:

1. Active mode: In active mode, the device actively sends LACP packets, advertising its willingness to form an aggregation. This mode enables a device to initiate the negotiation process with its connected peer.
2. Passive mode: In passive mode, the device does not initiate the negotiation process but can respond to LACP packets received from an actively participating peer. Passive mode devices only establish an aggregated link when connected to an active mode device.

PAGP Modes:

1. Desirable mode: Similar to LACP’s active mode, a device in desirable mode actively sends PAGP packets and is willing to form an aggregation with a connected peer. Desirable mode devices can establish aggregated links with both auto and desirable mode peers.
2. Auto mode: Auto mode in PAGP is analogous to LACP’s passive mode. Devices in auto mode do not initiate the negotiation process but can respond to PAGP packets received from a desirable mode peer. Auto mode devices only establish an aggregated link when connected to a desirable mode device.

When to Use Each Mode:

1. LACP active/passive or PAGP desirable/auto: Use these modes when you want to establish link aggregation between two devices, with one device initiating the negotiation process and the other device responding. This configuration is suitable when you want more control over which device initiates the aggregation process.
2. LACP active/active or PAGP desirable/desirable: Use these modes when you want both devices to actively participate in the negotiation process. This configuration provides faster convergence, as both devices can initiate the negotiation and form an aggregated link without waiting for the other device to initiate the process.

Conclusion:

Understanding the different modes of link aggregation is crucial for network administrators when designing and configuring networks for optimal performance, redundancy, and load balancing. By selecting the appropriate mode for each link, you can ensure that link aggregation is established efficiently and effectively, providing a more reliable and robust network infrastructure.