FortiGate IPsec Site‑to‑Site VPN (IKEv2) — Full CLI Setup, Verification, and Troubleshooting Guide

This step‑by‑step guide walks through configuring a route‑based IPsec site‑to‑site tunnel on FortiGate using FortiOS CLI (plus GUI notes), including Phase 1/Phase 2, routing, firewall policies, and verification. It also covers practical logging, troubleshooting commands, and defense best practices so SOC and network teams can validate secure connectivity and quickly triage tunnel issues