CCSM Advanced VPN Troubleshooting Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  To increase the speed of the tunnel encryption process.

  Why it's wrong here

  PFS actually decreases performance because it requires additional CPU-intensive Diffie-Hellman calculations during every re-key interval. It is a security feature, not a performance optimization, and is implemented to enhance the cryptographic strength of the session rather than speed up the packet processing.

• ✓

  To ensure that a compromised session key does not compromise future session keys.

  Why this is correct

  PFS forces a new key exchange for every re-key interval. Because the new key is not derived from the previous session key, the security of the current session is independent of the past, preventing an attacker from decrypting subsequent traffic if they manage to crack one session key.

• ✗

  To reduce the size of the VPN packets for better throughput.

  Why it's wrong here

  PFS has no impact on packet size. It involves the exchange of additional keying material during the re-key process, which might slightly increase the control plane traffic, but it does not affect the payload or the size of individual data packets passing through the tunnel.

• ✗

  To authenticate the peer using digital certificates instead of passwords.

  Why it's wrong here

  Authentication is handled by the IKE authentication phase, which can use certificates or pre-shared keys. PFS is strictly a key management feature related to session key derivation; it has no role in the identity verification of the VPN peers, which happens long before PFS is triggered.