SD-WAN Manual Strategy with SLA Failover for Voice Traffic
An SD-WAN rule is configured with a 'manual' strategy and multiple members. The engineer wants to ensure that voice traffic always uses the MPLS link as long as it meets the SLA, otherwise use the broadband link. Which configuration is required?
Quick Answer
The correct configuration is to set the manual strategy with MPLS as the first member and enable the SLA check. This works because a manual strategy with ordered members evaluates each link in sequence; the SD-WAN rule first attempts the MPLS link, and only if the SLA fails—meaning the link does not meet the defined performance thresholds for voice traffic—does it automatically fail over to the next member, typically the broadband link. On the Fortinet NSE 4 exam, this scenario tests your understanding of SD-WAN rule strategies and SLA-based failover, often appearing as a configuration question where you must distinguish between manual, best-quality, and load-balance strategies. A common trap is assuming that simply listing MPLS first without enabling the SLA check will enforce the failover, but without the SLA, the rule will not dynamically switch when the link degrades. Remember the memory tip: “Manual means ordered, SLA means conditional—first link if healthy, failover if not.”
⚠ Common exam trap
It's easy for candidates to confuse 'manual strategy' with 'best quality' strategy, assuming 'best quality' will always pick MPLS, but 'best quality' dynamically selects the best-performing link at any moment, which may not be MPLS if broadband has better SLA metrics.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the manual strategy with MPLS as first member and enable SLA check.
A manual strategy with ordered members and an SLA check allows the SD-WAN rule to first attempt the MPLS link; if the SLA is met, traffic uses MPLS, and if the SLA fails, the rule automatically fails over to the next member (broadband). This directly implements the engineer's requirement of 'MPLS if SLA met, otherwise broadband.'
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the strategy to 'volume' and configure MPLS as preferred.
Why it's wrong here
Incorrect; volume strategy is for load balancing, not failover.
- ✓
Set the manual strategy with MPLS as first member and enable SLA check.
Why this is correct
Correct; manual strategy with SLA check will use the first member if SLA is met, otherwise the next.
- ✗
Use 'load balancing' strategy and assign MPLS a higher weight.
Why it's wrong here
Incorrect; weight does not guarantee exclusive use.
- ✗
Set the strategy to 'best quality' and set MPLS with highest priority.
Why it's wrong here
Incorrect; best quality uses dynamic metrics, not fixed priority.
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Variation 1. A network engineer is configuring SD-WAN on a FortiGate with two WAN links: MPLS (port1) and Internet (port2). The MPLS link has lower latency and jitter. The engineer wants to route all VoIP traffic (SIP and RTP) over the MPLS link unless it is unavailable. Which SD-WAN rule configuration should be used?
medium- A.Create an SD-WAN rule for VoIP traffic with strategy 'best quality' and set the SLA target for latency to 10ms on the MPLS link.
- B.Create an SD-WAN rule for VoIP traffic with strategy 'load balancing' and assign equal weight to both links.
- ✓ C.Create an SD-WAN rule for VoIP traffic with strategy 'manual' or 'prefer' and select MPLS as the preferred member, with Internet as backup.
- D.Create an SD-WAN rule for VoIP traffic with strategy 'best quality' and set the SLA target to prefer the Internet link.
Why C: The engineer requires a deterministic routing policy where VoIP traffic always uses the MPLS link unless it fails. The 'manual' strategy in SD-WAN rules allows you to explicitly set a preferred member (MPLS) and designate the other link (Internet) as a backup, ensuring failover only when the preferred link is unavailable. This matches the requirement of routing all VoIP traffic over MPLS unless it is unavailable, without relying on SLA performance metrics.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This NSE4 practice question is part of Courseiva's free Fortinet certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the NSE4 exam.