Description
This article describes how 10G interfaces can be added to a LACP link-aggregation link.
Scope
FortiGate.
Solution
FortiGate units that support 10Gbps interfaces as well as link-aggregation (LACP 802.3ad) support the aggregation of interfaces of 1Gbps and 10Gbps even if they are of different speeds as mentioned on the RFC. The conditions they must comply are as follows:
- Interfaces must be free of non-default configuration before being added to the link-aggregation. By default 10Gbps interfaces are added as HA monitor interfaces. The 10Gbps interface must be removed from the HA monitor status before being added to the link-aggregation interface.
- The remote peer must allow this kind of connectivity (like another 10Gbps FortiGate unit with link-aggregation).
For a FortiGate Chassis, it is possible to create link aggregation groups (LAGs) that can include data interfaces from multiple FIMs and FPMs in the same chassis.
Guidelines for Link Aggregation Group Configuration.
It is important to adhere to specific best practices when configuring Link Aggregation Groups (LAGs) to ensure optimal performance and stability.
Interface Speed Homogeneity.
Mixing interfaces with disparate speeds (for example, 1 Gigabit per second (Gbps) with 10 Gbps) within a single Link Aggregation Group is strongly discouraged. While technically feasible in some implementations, such configurations often lead to unpredictable behavior, load balancing inefficiencies, and potential performance degradation.
Throughput Limitations.
Contrary to intuitive assumptions, the aggregate throughput of a LAG comprising mixed-speed interfaces will not simply be the sum of the individual interface speeds. Instead, the effective throughput will be constrained by the slowest interface within the group. This limitation results in underutilization of the higher-speed interfaces and an overall reduction in expected performance.
For instance, a LAG combining a 1 Gbps interface and a 10 Gbps interface will not achieve 11 Gbps of throughput; rather, its effective maximum throughput will be closer to 1 Gbps for any single flow, leading to inefficiencies.
Recommendation for Optimal Performance.
To achieve consistent load balancing, maximize throughput, and ensure robust network reliability, it is imperative to configure Link Aggregation Groups with interfaces of uniform speed. This practice mitigates potential issues associated with speed mismatches and ensures that the full capabilities of all aggregated interfaces are effectively leveraged.
