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NSE4 · Question #423

The exhibit shows a part output of the diagnostic command 'diagnose debug application ike 255', taken during establishment of a VPN. Which of the following statement are correct concerning this output

The correct answer is B. The output corresponds to a phase 2 negotiation D. The IP address of the remote IPsec VPN peer is 172.20.187.114. The diagnostic output from 'diagnose debug application ike 255' reveals details about the IPSec Phase 2 negotiation and identifies the remote peer's IP address.

Submitted by kim_seoul· Apr 18, 2026VPN and Routing

Question

The exhibit shows a part output of the diagnostic command 'diagnose debug application ike 255', taken during establishment of a VPN. Which of the following statement are correct concerning this output? (choose two)

Exhibit

NSE4 question #423 exhibit

Options

  • AThe quick mode selectors negotiated between both IPsec VPN peers is 0.0.0.0/32 for both
  • BThe output corresponds to a phase 2 negotiation
  • CNAT-T enabled and there is third device in the path performing NAT of the traffic between both
  • DThe IP address of the remote IPsec VPN peer is 172.20.187.114

How the community answered

(40 responses)
  • A
    5% (2)
  • B
    80% (32)
  • C
    15% (6)

Why each option

The diagnostic output from 'diagnose debug application ike 255' reveals details about the IPSec Phase 2 negotiation and identifies the remote peer's IP address.

AThe quick mode selectors negotiated between both IPsec VPN peers is 0.0.0.0/32 for both

Quick mode selectors like 0.0.0.0/32 for both ends would imply specific host-to-host tunnels and are not always the negotiated selectors; the actual selectors would need to be visible in the exhibit.

BThe output corresponds to a phase 2 negotiationCorrect

Messages such as 'quick mode' or 'Phase 2' in the IKE debug output directly indicate that the negotiation for data encryption SAs (Security Associations) is occurring, which is characteristic of IPSec Phase 2.

CNAT-T enabled and there is third device in the path performing NAT of the traffic between both

Determining if NAT-T is enabled and if a third device is performing NAT requires specific NAT-T negotiation messages and address translation details in the debug output, which is not stated to be present.

DThe IP address of the remote IPsec VPN peer is 172.20.187.114Correct

The debug output for IKE negotiations explicitly logs the IP addresses of both the local and remote VPN peers involved in the communication, making the remote peer's IP address (172.20.187.114) identifiable.

Concept tested: FortiGate IPSec IKE Debug Output Analysis

Source: https://docs.fortinet.com/document/fortigate/7.4.0/administration-guide/603403/troubleshooting-ipsec-vpns

Topics

#IPsec VPN#IKE Negotiation#FortiGate CLI#Troubleshooting

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