''If SD-WAN is disabled, you can change the ECMP load balancing algorithm on the FortiGate CLI using the commands shown on this slide.''

''When SD-WAN is enabled, FortiOS hides the v4-ecmp-mode setting and replaces it with the load-balance-mode setting under config system sdwan. That is, when you enable SD-WAN, you control the ECMP algorithm with the load-balance-mode setting.''

''There are some differences between the two settings. The main difference is that load-balance-mode supports the volume algorithm, and v4-ecmp-mode does not.''

''These routes are called equal cost multipath (ECMP) routes...''

Technical Deep Dive:

The correct answers are A and D.

A is correct because when SD-WAN is enabled, FortiOS no longer uses v4-ecmp-mode; it uses load-balance-mode under config system sdwan. That is the explicit SD-WAN control point for ECMP behavior.

D is correct because when SD-WAN is disabled, ECMP configuration is done in the regular system routing settings, not under SD-WAN. The study guide states that you change the ECMP algorithm on the FortiGate CLI when SD-WAN is disabled, which corresponds to the classic config system settings ECMP controls.

Why the others are wrong:

B is wrong because the guide explicitly says load-balance-mode supports volume, while v4-ecmp-mode does not. So you cannot set v4-ecmp-mode to volume-based.

C is wrong because ECMP requires equal-cost routes. If distance or priority differ, they are no longer ECMP candidates; FortiGate selects the preferred route instead. The concept of ECMP itself requires equal route cost attributes.

From an implementation standpoint, the common CLI patterns are:

config system settings

set v4-ecmp-mode source-ip-based

end

and, with SD-WAN enabled:

config system sdwan

set load-balance-mode source-ip-based

end

On hardware platforms, ECMP still affects session distribution at the routing decision stage before later security services are applied. NP offload can accelerate forwarding after route selection, but the ECMP decision itself is a FortiOS control-plane routing function.