NSE4 Question #42: Real Exam Question with Answer & Explanation

Question

Review the IKE debug output for IPsec shown in the exhibit below. Which statements is correct regarding this output?

Options

• AThe output is a phase 1 negotiation.
• BThe output is a phase 2 negotiation.
• CThe output captures the dead peer detection messages.
• DThe output captures the dead gateway detection packets.

Explanation

The IKE debug output for IPsec in the exhibit is showing messages related to Dead Peer Detection (DPD), which is used to monitor the liveness of the VPN peer.

Common mistakes.

• A. IKE Phase 1 negotiation debug output would show exchanges related to security association establishment, key exchange, and authentication, which are distinct from DPD messages.
• B. IKE Phase 2 negotiation debug output would display information about the IPsec Security Association (SA) establishment, including Quick Mode exchanges and traffic selector negotiation, not DPD messages.
• D. While DPD helps detect a 'dead gateway,' the specific term 'dead gateway detection packets' is not standard in IPsec debug output; the mechanism is called Dead Peer Detection.

Concept tested. IPsec IKE debug interpretation (DPD)

Reference. https://docs.fortinet.com/document/fortigate/7.4.0/cli-reference/169096/config-vpn-ipsec-phase1-interface

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