SD-WAN Rule for Voice Traffic
An administrator wants to ensure that voice traffic (UDP 16384-32768) always uses the MPLS link, while internet-bound traffic uses broadband. Which SD-WAN feature should be configured to achieve this?
Quick Answer
The answer is an SD-WAN rule. This is the correct choice because SD-WAN rules are specifically designed to match traffic based on criteria like source, destination, or port numbers, and then enforce a path selection strategy—such as manual or best quality—to steer that traffic to a preferred member, like the MPLS link. For voice traffic using UDP 16384-32768, the rule can match that port range and set the strategy to force all matching packets over the MPLS interface, while leaving other internet-bound traffic to use broadband. On the Fortinet NSE 7 Advanced Security NSE7 exam, this tests your understanding of how SD-WAN rules differ from simple static routes or policy-based routing; a common trap is confusing SD-WAN rules with firewall policies, which handle security rather than path selection. Remember the tip: "Rules route, policies protect"—if you need to force a specific traffic type over a specific link, you configure an SD-WAN rule, not a firewall policy.
⚠ Common exam trap
A common mix-up: candidates confuse Performance SLA (which monitors and reacts to link quality) with the policy engine that actually decides which traffic goes where, leading them to select option A instead of the correct SD-WAN rule.
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
✓
SD-WAN rule
SD-WAN rules (option D) allow administrators to define policy-based forwarding by matching specific traffic characteristics—such as UDP ports 16384-32768 for voice—and steering that traffic to a preferred interface or link (e.g., the MPLS link). This is the correct feature because it directly controls traffic steering based on application or service, overriding any default load-balancing or failover behavior.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Performance SLA
Why it's wrong here
Performance SLA monitors link quality and steers traffic when thresholds are breached; it cannot classify UDP 16384-32768 as voice or pin it to MPLS. It is tempting because SLA rules do influence path selection, but they act on measured latency, jitter and packet loss, not on application identity.
- ✗
SD-WAN member configuration
Why it's wrong here
SD-WAN member configuration defines each link's participation, cost and priority, but does not itself match traffic by port range to steer voice onto MPLS. It is tempting because members are the links being selected, and it would be correct if the requirement were simply adding or removing a member from the SD-WAN.
- ✗
Load balancing algorithm
Why it's wrong here
Load balancing distributes sessions across members by weight or algorithm; it cannot guarantee that UDP 16384-32768 always traverses the MPLS link. It is tempting because it governs path selection across SD-WAN members, and it would be correct if the goal were spreading traffic evenly rather than pinning voice to one link.
- ✓
SD-WAN rule
Why this is correct
An SD-WAN rule matches traffic by application or UDP port range and directs it to a preferred member, so voice (UDP 16384-32768) can be pinned to the MPLS link while internet-bound traffic egresses broadband, satisfying the required path separation.
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Variation 1. An organization is deploying SD-WAN across multiple sites with two internet links (MPLS and broadband) at the main branch. They want voice traffic to use the MPLS link unless it fails, in which case failover to broadband should occur. Which SD-WAN rule configuration achieves this?
medium- A.Configure an SD-WAN rule for voice with strategy 'maximize bandwidth' and members MPLS and broadband.
- B.Configure an SD-WAN rule for voice with strategy 'lowest cost' and members MPLS and broadband.
- ✓ C.Configure an SD-WAN rule for voice with strategy 'best quality', set MPLS as preferred member, and define SLA targets for MPLS.
- D.Configure an SD-WAN rule for voice with strategy 'manual' and members MPLS and broadband.
Why C: The 'best quality' strategy with a preferred member and SLA targets allows voice traffic to use the MPLS link as long as it meets the defined SLA (e.g., latency, jitter, packet loss). If the MPLS link fails or degrades below the SLA threshold, the SD-WAN rule automatically fails over to the broadband link, ensuring voice traffic continuity.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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