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. A deployment should preserve the distinction between the physical or logical WAN underlay, the IPsec overlay and the SD-WAN zone that groups forwarding members. These layers can have different routing and security-policy requirements. The configured architecture must also allow the required traffic paths and failover behavior rather than assuming every available interface is interchangeable. Before applying a topology change, review the interface dependencies, static and dynamic routing, security policies and provisioning templates. FortiGate can support multiple transport types, but routing and tunnel compatibility still determine whether the intended member is operationally eligible. In the relevant Fortinet FortiOS documentation, the applicable feature should be verified against the deployed software version, the selected configuration mode and the live operational state before the answer is treated as a definitive implementation requirement.