This IPsec Phase 1 configuration defines a dynamic VPN tunnel that can accept connections from multiple peers. The settings chosen here suggest a configuration optimized for networks with intermittent traffic patterns while ensuring resources are used efficiently.
Key configurations and their impact:
* set type dynamic → This allows multiple peers to establish connections dynamically without needing predefined IP addresses.
* set ike-version 2 → Uses IKEv2, which is more efficient and supports features like EAP authentication and reduced rekeying overhead.
* set dpd on-idle → Dead Peer Detection (DPD) is triggered only when the tunnel is idle, reducing unnecessary keep-alive packets and improving resource utilization.
* set add-route enable → FortiGate automatically adds the route to the routing table when the tunnel is established, ensuring connectivity when needed.
* set proposal aes128-sha256 aes256-sha256 → Uses strong encryption and hashing algorithms, ensuring a secure connection.
* set keylife 28800 → Sets a longer key lifetime (8 hours), reducing the frequency of rekeying, which is beneficial for stable connections.
Because DPD is set to on-idle, the tunnel will not constantly send keep-alive messages but will still ensure connectivity when traffic is detected. This makes the configuration ideal for networks with regular but non-continuous traffic, balancing security and resource efficiency.

From the exhibit, ISFW is part of a Security Fabric environment with NGFW-1 as the Fabric Root. In this architecture, FortiGate devices share security intelligence, including logs and detected threats.
ISFW is in a Security Fabric environment:
# Security Fabric allows devices like ISFW to receive threat intelligence from NGFW-1, even if UTM is not enabled locally.
# If NGFW-1 detects malware from IP 10.1.10.1 to 89.238.73.97, this information can be propagated to ISFW and FortiAnalyzer.
The firewall policy in NGFW-1 has UTM enabled:
# Even though ISFW does not have UTM enabled, NGFW-1 (which sits between ISFW and the external network) does have UTM enabled and is scanning traffic.
# Since NGFW-1 detects malware in the session, it logs the event, which is then sent to FortiAnalyzer.

In this scenario, the corporate network and the new remote office network need to communicate over the Internet, which requires a secure and dynamic routing method. Since both networks are using OSPF (Open Shortest Path First) as the routing protocol, the best approach is to establish an OSPF over IPsec VPN to ensure secure and dynamic route propagation.
OSPF is already running on the corporate network, and extending it over an IPsec tunnel allows dynamic route exchange between the corporate FortiGate and the remote office FortiGate. IPsec provides encryption for traffic over the Internet, ensuring secure communication. OSPF over IPsec eliminates the need for manual static routes, allowing automatic route updates if networks change.
The new remote office's 192.168.1.0/24 subnet will be advertised dynamically to the corporate network without additional configuration.