What is used to determine the hashing algorithm for load balancing across a LAG in Aruba OS-CX switches?

In Aruba OS-CX switches, the hashing algorithm for load balancing across a Link Aggregation Group (LAG) primarily utilizes Layer-4 TCP/UDP port numbers. This approach is effective because it allows the switch to make more granular decisions about how to distribute traffic across the multiple links in a LAG. By considering both Layer-3 IP addresses and Layer-4 ports, the switch can differentiate between separate sessions and provide load balancing based on individual conversations.

While the Layer-3 Source and Destination IP addresses can also play a role in the hashing process, they typically don’t provide enough granularity for effective load distribution when multiple connections from the same source to the same destination are involved. Similarly, Layer-2 MAC addresses can be part of the hashing algorithm, but they are generally less effective for distinguishing traffic flows compared to Layer-4 information. Layer-1, referring to the physical layer, does not pertain to hashing algorithms and is not involved in traffic distribution decisions at the switch level.

Thus, relying on Layer-4 TCP/UDP ports as the main consideration allows for a more effective load balancing strategy that optimizes the utilization of the aggregated links.