Port Aggregation FAQs

What is the benefit of aggregating ports? 

Port aggregation can increase maximum throughput, and allow for network redundancy. It does this by splitting traffic across multiple ports instead of forcing clients to use a single uplink port on a switch. Note that these performance improvements will only occur when multiple clients are passing traffic simultaneously through the aggregated ports.

Who may be interested in aggregation?

Most home-users do not need this, but enterprise users will see the benefit both from the increased throughput, as well as the redundancy it provides.

What devices support port aggregation?

All UniFi Switches support aggregation, except USW-Flex, USW-Flex-Mini and USW-Ultra.

Port aggregation is not supported on UniFi Gateways. Because of this, you should not aggregate two ports connected from a UniFi Switch to a UniFi Gateway.

What are the use cases for aggregation?

1. Switch-to-Switch Aggregation: This is useful in scenarios where you need to interconnect multiple switches to increase the bandwidth available between them and ensure network redundancy. It helps in managing higher traffic loads between switches.

2. Switch-to-Client Aggregation: This is beneficial when a single client device, such as a high-performance server, requires more bandwidth than a single port can provide. Aggregating ports can split the traffic load and increase the overall throughput available to the client.

What are the limitations of aggregation?

• Ports must be sequential in number.
• Static LAG configurations are not supported, only LACP (802.3ad).
• Multi-chassis Link Aggregation Group (MLAG) is not supported.

What cable should I consider for gateway-to-aggregation switch connections?

For maximum throughput in gateway-to-aggregation switch connections, it is recommended to use SFP+.

What is the difference between static LAG configurations and LACP?

• Static LAG (Link Aggregation Group) Configurations: These require manual configuration on both ends of the link, which can be prone to misconfiguration and do not provide automatic failover.
• LACP (Link Aggregation Control Protocol): LACP is an industry-standard protocol (802.3ad) that dynamically manages link aggregation, provides automatic failover, and helps prevent misconfigurations by ensuring both ends of the link agree on the aggregation settings.

In what order should I configure port aggregation on my switches?

You should be certain that configuration changes are first done on the most downstream switch, and then move upstream towards your UniFi Console.

What is MC-LAG, and how is it different from standard port aggregation?

MC-LAG (Multi-Chassis Link Aggregation Group) allows two switches to work together as a single logical unit, providing both load balancing and redundancy. This setup ensures minimal downtime by enabling other switches or servers to connect to both MC-LAG switches at once.

For large networks needing higher resilience and performance, MC-LAG offers a more advanced alternative to standard port aggregation. To learn how to configure an MC-LAG setup, see this guide.