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Difficulty: MediumVirtual Private Networks and Remote Access Security

A network security administrator is configuring an IPsec Remote Access VPN using IKEv1 Main Mode. Place the four primary operational steps of the IKE handshake process into the correct chronological sequence from start to finish.

  1. 1Negotiation of ISAKMP policy parameters (encryption algorithm, hash algorithm, DH group, and authentication method).
  2. 2Diffie-Hellman key exchange and transmission of random nonces to generate shared secret keys.
  3. 3Peer identity authentication and verification over the newly encrypted Phase 1 tunnel.
  4. 4Quick Mode negotiation to establish Phase 2 IPsec Security Associations (SAs) for protecting user payload data.

Answer

The correct sequential order for establishing an IPsec VPN tunnel using IKEv1 is: 1) Negotiate ISAKMP policy parameters, 2) Perform Diffie-Hellman key exchange and nonce generation, 3) Authenticate peer identities to complete Phase 1, and 4) Execute Quick Mode to establish Phase 2 IPsec SAs for data traffic.
The correct order follows the standard 6-message Phase 1 exchange followed by Phase 2 Quick Mode: initial ISAKMP policy proposal matching, Diffie-Hellman public key and nonce exchange, encrypted identity authentication, and finally Quick Mode negotiation of IPsec SAs for data transport.

Step-by-Step Solution

1
Identify the initial policy negotiation phase.
The client and gateway negotiate policy proposals covering symmetric cipher, hashing algorithm, authentication type, and DH group.
End-points must agree on baseline cryptographic algorithms before initiating key exchange.
2
Identify the shared secret key generation phase.
Endpoints exchange Diffie-Hellman values and nonces to compute shared symmetric keys (SKEYID).
Diffie-Hellman key exchange provides the secret key material required to secure subsequent authentication messages.
3
Identify the peer authentication phase.
End-device identities (IP addresses or certificates) are transmitted and validated, completing Phase 1 (ISAKMP SA).
Main Mode protects identity privacy by encrypting authentication payloads with the DH-derived keys.
4
Identify the Phase 2 IPsec SA establishment phase.
Quick Mode negotiates payload protection parameters (such as ESP encryption and hash mechanisms) to build the data-plane IPsec tunnel.
Phase 2 utilizes the secure ISAKMP SA management tunnel established in Phase 1 to safely negotiate data-plane protection.

Key Concept

IPsec IKEv1 Phase 1 and Phase 2 Handshake Sequence
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Topics

Virtual Private Networks and Remote Access Security

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