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Difficulty: MediumRemote Access and Site-to-Site VPN Concepts

Match each IPsec VPN framework component or feature on the left with its correct primary operational function on the right.

  • Internet Key Exchange (IKE)Negotiates security parameters, authenticates VPN peers, and manages Security Associations (SAs).
  • Encapsulating Security Payload (ESP)Provides data confidentiality via encryption, along with data integrity and origin authentication for IP payloads.
  • Diffie-Hellman (DH) GroupEnables VPN peers to securely derive a shared symmetric encryption key over an untrusted public network.
  • NAT Traversal (NAT-T)Encapsulates IPsec ESP packets inside UDP port 4500 to allow traffic to traverse intermediate PAT devices.

Answer

Internet Key Exchange (IKE) pairs with negotiating security parameters, authenticating peers, and managing SAs. Encapsulating Security Payload (ESP) pairs with providing data confidentiality, data integrity, and origin authentication for IP payloads. Diffie-Hellman (DH) Group pairs with enabling peers to securely derive a shared symmetric encryption key over an untrusted network. NAT Traversal (NAT-T) pairs with encapsulating ESP packets inside UDP port 4500 to traverse intermediate PAT devices.
Each IPsec component fulfills a distinct cryptographic or transport requirement: IKE handles control-plane negotiations and SA creation; ESP encrypts data payload and validates integrity; Diffie-Hellman allows safe secret derivation over public IP backbones; and NAT-T wraps ESP into UDP port 4500 so port address translation devices do not drop or modify the encrypted traffic.

Step-by-Step Solution

1
Identify the control plane protocol responsible for authentication, parameter negotiation, and Security Association (SA) management.
Match Internet Key Exchange (IKE) with SA negotiation and peer authentication.
IKE (v1 or v2) is specifically responsible for establishing control channels and negotiating cryptographic sets (SAs).
2
Distinguish between data protection mechanisms and key exchange mechanisms within the IPsec suite.
Match Encapsulating Security Payload (ESP) with data encryption and integrity, and Diffie-Hellman (DH) with shared key calculation.
ESP (IP protocol 50) encrypts user data, while DH public-key exchange algorithms generate matching symmetric keys on both endpoints.
3
Determine the solution used to overcome IPsec header modification issues caused by address translation devices.
Match NAT Traversal (NAT-T) with UDP port 4500 encapsulation.
Because ESP headers lack Layer 4 port numbers required for PAT, NAT-T inserts a UDP port 4500 header in front of the ESP packet.

Key Concept

IPsec VPN Protocol Framework and NAT Traversal Operations
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Topics

Remote Access and Site-to-Site VPN Concepts

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