Hello everyone,
As shown in Figure 1, RouterA and RouterB are connected.
Interface1 is the primary interface.
Interface2 and interface3 are backup interfaces.

Backup interfaces become unavailable after the primary interface fails.
In load balancing mode, load balancing cannot be implemented among the primary and backup interfaces because they cannot all be in Up state simultaneously.
In load balancing mode, traffic cannot be load balanced among multiple interfaces.
This fault is commonly caused by one of the following:
The physical status of backup interfaces is Down.
The link layer status of backup interfaces is Down.
In load balancing mode:
The load balancing threshold and maximum bandwidth are not configured for the primary interface.
An equal-cost route is not generated.
Only one flow needs to be transmitted.
That is all I want to share with you! Thank you!