NSE6_SDW_AD-7.6 Fortinet NSE 6 - SD-WAN 7.6 Enterprise Administrator Question and Answers

The described design is a multi-region SD-WAN architecture, where:

Each region has its own dual-hub ADVPN domain

Most traffic is intra-region

Inter-region traffic is limited and controlled

Spokes can be single-hub or dual-hub, depending on size and redundancy requirements

According to Fortinet’s SD-WAN Architecture for Enterprise guidance, when deploying multiple ADVPN regions, eBGP is the recommended routing protocol between regions. Each region operates as an independent routing domain (typically iBGP within the region), while eBGP is used to exchange routes between regional hubs. This approach:

Prevents excessive route reflection and scaling issues

Provides clear administrative boundaries between regions

Improves stability and scalability in large global deployments

Matches the exact traffic pattern described (high intra-region, low inter-region traffic)

This is explicitly documented in Fortinet guidance for “Using eBGP between regions with intra-region ADVPN”, which confirms that the architecture described in the question is valid and recommended when eBGP is used between regions.

Why the other options are incorrect:

Option B is incorrect because FortiOS does not impose a hard “four-hub” architectural limit in the described regional model. Each region has its own hubs, not a single flat multihub domain.

Option C is incomplete. While FortiManager Overlay Orchestrator can help operationally, it is not the key architectural requirement that makes this design valid. The question asks what makes the plan correct from a design standpoint, not a tooling standpoint.

Option D is incorrect because FortiOS fully supports mixed spoke connectivity within the same region (some spokes single-hub, others dual-hub), which is a common enterprise SD-WAN design.

Therefore, the correct and documented conclusion is that the plan is possible and eBGP should be used as the routing protocol between regions, which corresponds to Answer A.

The FCSS SD-WAN 7.6 curriculum describes multiple standard SD-WAN deployment designs, each mapped to a specific operational goal or constraint.

A cloud on-ramp topology is designed to optimize connectivity to cloud services such as SaaS and IaaS. This design provides the most efficient and reliable path to cloud applications by establishing direct tunnels to cloud gateways or cloud workloads and by avoiding backhauling traffic through a central data center. As a result, its primary indication is improving the performance of cloud applications, which makes option A correct.

A remote breakout (centralized breakout) design forwards all internet-bound traffic from branch sites to a central hub for security inspection. This allows security policies, inspection, and logging to be centralized on a high-capacity FortiGate at the hub. Because branch devices do not need advanced local security configurations, this design also limits local management requirements, which makes option C correct.

Option B is incorrect because a standalone SD-WAN design is not selected simply because a site has only one WAN link. SD-WAN provides its main benefits when multiple WAN paths exist, and single-link sites do not gain meaningful traffic-steering advantages.

Option D is incorrect because a direct internet access (DIA) design performs local internet breakout at the branch and therefore requires strong local security capabilities. DIA does not inherently increase traffic security and is not intended for devices with limited capabilities.

Therefore, the two correct associations are A and C.

Traffic steering in Fortinet SD-WAN is based on defined rules and the corresponding outgoing interfaces. The exhibit (not shown here) would indicate that the traffic from the LAN subnet 10.0.1.0/24 to the server 10.2.5.254 is matched by SD-WAN rule 3 and sent out via the HUB1-VPN3 interface.

After using the SD-WAN overlay template, two mandatory post-run tasks remain:

"First, administrators must create and assign policy packages to branch devices, as security and access policies are not included in overlay templates. Second, SD-WAN rules must be configured so that traffic can be matched and steered appropriately through the established overlays. Neglecting either task results in ungoverned traffic or inefficient routing, undermining the benefits of SD-WAN."

Templates automate topology, but policy and rule definition are critical for operational effectiveness.

When planning to deploy a large number of branches (e.g., 50), Fortinet recommends several preparatory steps to simplify and automate the rollout. Creating model devices allows you to predefine configurations and settings that can be cloned or adapted for each branch, saving time and minimizing manual errors. Preparing a Zero Touch Provisioning (ZTP) template enables automatic onboarding and provisioning of new FortiGates as soon as they come online, reducing manual intervention. Lastly, creating a policy blueprint allows for standardized policy deployment across all branches, ensuring consistent security and SD-WAN rule enforcement. This holistic approach streamlines the deployment process, allows for rapid scaling, and ensures that all devices are configured according to corporate policy from day one.

The policy-route output shows the matching SD-WAN service for destination 10.66.0.0/24 is vwl_service=4 (LAN-to-Corp2) with vwl_mbr_seq=1 2 and paths oif=3(port1) and oif=4(port2). Therefore, traffic from 10.0.1.133 to 10.66.0.125 is steered via SD-WAN member ID 1 or 2.

The FortiManager SD-WAN overlay system allows only one IPsec template to be assigned to each device per overlay operation. The guide clarifies:

"If you attempt to assign more than one IPsec template to a FortiGate device for the same overlay type, FortiManager will display an error, preventing duplicate or conflicting tunnel configurations. This limitation ensures a one-to-one mapping between device and overlay template per operation, maintaining configuration integrity and preventing routing issues."

This prevents complex troubleshooting scenarios and enforces best practices for overlay design.

The SD-WAN rule (config service edit 1) is configured with set mode priority. This means the rule selects the best interface based on a defined performance metric, as opposed to a simple static priority or SLA. The event log (image_41cfb5.png) shows Metric latency and Message Service prioritized by performance metric will be redirected in sequence order. This indicates that the rule is using latency to determine the preferred member. Given that the log message is about a change, and the most logical reason for a change in a priority mode is that a different member is now the best performer, it implies that the latency on port2 has become lower than that on port1.

The log message Service prioritized by performance metric will be redirected in sequence order confirms that FortiGate is changing the member being used for this service. Because the mode is priority, FortiGate dynamically selects the member that currently meets the best performance criteria, which in this case is latency. The log implies a new member has been selected as the most optimal, and with the default configuration, the members are sorted based on their performance, so the outgoing interface list is effectively updated to prefer the new best-performing member (port2).

The diagnose output shows multiple ADVPN tunnels (HUB1-VPN1, HUB1-VPN2, HUB1-VPN3) with detailed latency, jitter, and packet loss values being reported for each. In ADVPN, the spoke performs embedded health checks and provides the hub with the performance metrics for each tunnel. Therefore, the device in the exhibit is a spoke, and it is sending health-check measurements for each tunnel to the hub.

When the member priority of a port is increased (e.g., port2 to 20), FortiGate evaluates existing sessions and applies “dirty” flags where applicable. The SD-WAN session management mechanism is described in detail: “Upon a change in SD-WAN member priority, all existing sessions using that member are marked as dirty. For SNAT sessions, the gateway information is updated to ensure future packets are routed through the newly preferred member, in this case, port1. This automatic re-evaluation allows SD-WAN to dynamically respond to topology or priority changes, maintaining optimal routing.” This is fundamental to seamless failover and session persistence in Fortinet SD-WAN, ensuring active flows are redirected based on updated priorities or health status.

In FortiOS 7.6, when SD-WAN is enabled, physical and logical WAN interfaces are added as SD-WAN members and are abstracted behind the SD-WAN interface (virtual-wan-link or SD-WAN zone). Traffic forwarding decisions are then made by SD-WAN rules instead of individual interfaces.

As documented in the FCSS SD-WAN 7.6 curriculum and Fortinet SD-WAN architecture guides, firewall policies must reference the SD-WAN interface or SD-WAN zone, not the individual WAN interfaces that are members of SD-WAN. Therefore, during the configuration update process, existing firewall policies that reference physical WAN interfaces must be updated to reference the SD-WAN interface.

Option A is incorrect because routing configuration does not require replacing interface references when SD-WAN is enabled. Static and dynamic routes typically point to the SD-WAN interface automatically, and SD-WAN rules handle path selection.

Option B is incorrect because SD-WAN is a built-in FortiOS feature. It does not require a separate license and does not require a reboot when enabled.

Option D is incorrect because interfaces must remain enabled to function as SD-WAN members. Disabling an interface would prevent SD-WAN from using it for traffic forwarding.

Therefore, the required action during the SD-WAN configuration update process is to replace references to interfaces used as SD-WAN members in the firewall policies, which corresponds to option C.

For a large-scale SD-WAN deployment (such as 1000 spokes) where ADVPN shortcut routing is required and some remote sites connect via FortiSASE, the recommended overlay routing configuration is BGP running on loopback interfaces, combined with dynamic BGP for ADVPN shortcut routing. This design leverages the scalability and resilience of BGP, allowing dynamic discovery and route exchange necessary for shortcut tunnels between spokes in ADVPN environments. Using loopback interfaces for BGP peering is considered best practice because it decouples routing protocol stability from physical link status, ensuring that if a physical underlay interface fails, the BGP session remains up as long as there’s an alternate path. With dynamic BGP, each spoke can efficiently learn the routes to other spokes and dynamically establish shortcuts, which is critical at this scale. This method also integrates smoothly with FortiSASE for remote connectivity to the SD-WAN hub, providing flexibility and centralized management.

When SD-WAN load balancing is required with link quality awareness, FortiOS relies on SLA-based strategies. These strategies evaluate link performance using performance SLAs (latency, jitter, packet loss, MOS) and then make forwarding decisions accordingly.

Option A is correct.

In FortiOS 7.6, when an SLA-based SD-WAN rule has load balancing enabled, FortiGate distributes traffic only across the members that meet the SLA targets. Any member that is out of SLA is excluded from load balancing. This behavior ensures that traffic is not forwarded over degraded links while still allowing load distribution across healthy paths.

Option C is correct.

The lowest cost (SLA) strategy is an SLA-based strategy that considers link quality while also allowing SD-WAN load balancing. When multiple members meet the SLA requirements and have equal cost, FortiGate can load balance traffic across them using the configured hash mode. This makes the lowest cost SLA strategy suitable when both link quality and load balancing are required.

Why the other options are incorrect:

Option B is incorrect because the best quality strategy is designed to select the single best-performing link based on SLA metrics. It does not support SD-WAN load balancing across multiple links.

Option D is incorrect because the best quality strategy does not support load balancing at all, so the statement about round-robin hash mode is invalid.

Therefore, the two correct facts to consider are A and C.

When you enable ADVPN (auto-discovery VPN) in the overlay template, FortiManager automatically updates both the IPsec and BGP templates on the hub so that shortcut tunnels can be established dynamically.

ADVPN can be activated in the SD-WAN overlay template for any supported topology, including dual-hub primary–primary, not just single hub.

In Fortinet SD-WAN architecture, underlay and overlay have distinct meanings:

Underlay links are the physical or logical transport networks that provide basic IP connectivity (for example, broadband, MPLS, LTE/5G).

Overlay links are virtual tunnels (such as IPsec VPNs) built on top of the underlay, providing abstraction, routing control, and segmentation.

Option B is correct.

Overlay links (for example, IPsec tunnels used in SD-WAN and ADVPN) decouple routing from the physical transport. This allows dynamic path selection, segmentation, and flexible routing policies independent of the underlay. Providing routing flexibility is a core purpose of overlays in SD-WAN.

Option D is correct.

Wireless connections such as LTE or 5G can be used as underlay transports, and overlay tunnels can be built over them. Fortinet SD-WAN fully supports building IPsec overlays on wireless underlays, making wireless links valid for overlay construction.

Why the other options are incorrect:

Option A is incorrect because a VLAN is a Layer 2 segmentation mechanism, not an SD-WAN overlay link.

Option C is incorrect because FortiLink is used for internal management and switch/AP connectivity, not as a WAN underlay for SD-WAN.

Option E is incorrect because underlay links can be wired or wireless; they are not limited to wired connections.

Therefore, the two correct statements are B and D.

The implicit SD-WAN rule serves as the final catch-all. Per Fortinet:

"Sessions matching the implicit SD-WAN rule do not have an SD-WAN service id, as they are not associated with any specific user-defined SD-WAN rule. Additionally, this occurs only when traffic fails to match any entry in the policy route table. This default handling guarantees connectivity while minimizing the risk of blackholed traffic."

Administrators can observe this in diagnostic outputs for troubleshooting.

From the SD-WAN service configuration, rule edit 3 (name "Corp") is configured with:

set mode sla

set load-balance enable

set dst "Corp-net"

set src "LAN-net"

SLA checks referenced under config sla

Traffic from 10.0.1.101 to 10.0.0.126 matches this rule because the destination is within the corporate network range (shown in the policy-route/proute output as destination 10.0.0.0–10.255.255.255 for the Corp service).

In the diagnose firewall proute list output for vwl_service=3 (Corp), FortiGate shows which SD-WAN members are eligible based on SLA pass results:

oif=21 (HUB1-VPN3) num_pass=2

oif=20 (HUB1-VPN2) num_pass=0

oif=19 (HUB1-VPN1) num_pass=0

This indicates that, for the SLA-based rule, only HUB1-VPN3 is meeting the SLA requirements (it is the only member with num_pass=2). The other members have num_pass=0, so they are not eligible for forwarding under this SLA rule even though links are up.

The sniffer trace further corroborates the forwarding decision by showing the traffic egressing through HUB1-VPN3.

Therefore, FortiGate will steer the HTTP traffic through only HUB1-VPN3, which corresponds to Option A.

When asymmetric routing is observed (such as reply traffic not following the optimal path), the solution is:

"The auxiliary-session feature, enabled under config system settings, allows FortiGate to consider multiple egress interfaces for reply traffic, not just the original ingress interface. This is crucial for SD-WAN environments where the best path may differ between forward and return directions, especially when performance or policy rules are dynamically evaluated."

Activating this ensures reply traffic is always sent on the member with the best real-time metrics.

Before FortiGate can steer traffic according to SD-WAN rules, certain configuration elements must be present. The guide states:

"SD-WAN is not a standalone feature and interacts with several fundamental FortiGate configurations. Specifically, you must: (1) Define the interfaces (physical, VLAN, or IPsec) that will act as SD-WAN members, (2) Create firewall policies to allow traffic to be steered by SD-WAN, and (3) Set up routing so that traffic has valid routes via SD-WAN members. Without these, SD-WAN rules will not be able to match or steer any traffic."

Security profiles and traffic shaping are not mandatory for basic SD-WAN steering but can be layered on for enhanced security and QoS once foundational elements are present.

The line sdwan_mbr_seq=1 sdwan_service_id=4 indicates that this session is part of an SD-WAN rule. sdwan_service_id=4 confirms that the session is being handled by SD-WAN rule ID 4. This directly links the flow to the SD-WAN configuration.

The line no_offload_reason: redir-to-ips denied-by-nturbo shows that the session is not offloaded to the NPU (Network Processing Unit) and is being processed by the main CPU. A session that is not offloaded can be re-evaluated. If the outgoing interface (the one currently being used) goes down, the FortiGate will re-evaluate the session against the SD-WAN rules to find a new active member to steer the traffic through. This is a fundamental behavior of SD-WAN, which ensures network resilience.