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Within ADVPN topologies, shortcut requests and responses traverse spokes and hubs. Fortinet documentation states:

"When a spoke receives a shortcut query from another spoke, it may forward the response to its hub for validation or to facilitate dynamic shortcut tunnel setup. This mechanism allows direct spoke-to-spoke communication for optimized routing and performance, reducing latency and offloading the hub after initial control-plane mediation."

This is a core benefit of ADVPN’s dynamic shortcut feature.

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.

FortiManager enforces a strict distinction:

"Firewall policies must reference SD-WAN zones, not individual SD-WAN members, when used in conjunction with SD-WAN templates. Attempting to install a policy that references a specific member (interface) will result in a deployment error, as member-level targeting is not supported in SD-WAN policy abstraction. This enforces centralized policy consistency and proper SD-WAN operation."

Ensuring policies target zones allows FortiGate to dynamically select the optimal member.

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.

Application-based SD-WAN rules enable intelligent traffic steering. The guide specifies:

"If a flow is identified as belonging to a defined application category (such as social media), FortiGate will match it to the corresponding service rule (rule 2) and route it through the specified interface, such as port2. However, if the application is not recognized during the session setup, the system defaults to load balancing the traffic using the available tunnels according to the policy for unclassified traffic, ensuring continuous connectivity while waiting for application classification."

This guarantees both performance and resilience.

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 an SD-WAN member is deleted, FortiGate can also remove static routes that were tied to that interface. If those routes are needed for destinations not covered by SD-WAN rules, traffic to those networks becomes unreachable. This explains why flows not matching SD-WAN rules are interrupted after the member was removed.