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NSE4 · Question #417

How many packets are interchanged between both IPSec ends during the negotiation of a main- mode phase 1?

The correct answer is D. 6. In IKEv1 main mode, establishing a secure channel for subsequent data encryption involves a six-packet exchange between the two IPSec peers.

Submitted by noor.lb· Apr 18, 2026VPN and Routing

Question

How many packets are interchanged between both IPSec ends during the negotiation of a main- mode phase 1?

Options

  • A5
  • B3
  • C2
  • D6

How the community answered

(22 responses)
  • C
    5% (1)
  • D
    95% (21)

Why each option

In IKEv1 main mode, establishing a secure channel for subsequent data encryption involves a six-packet exchange between the two IPSec peers.

A5

5 packets is incorrect; IKEv1 main mode specifically uses 6 packets for its secure negotiation process.

B3

3 packets typically refers to IKEv1 aggressive mode, which is a faster but less secure negotiation method.

C2

2 packets is insufficient for the multi-step process required to establish a secure Phase 1 IKEv1 main mode session.

D6Correct

IKEv1 main mode negotiation consists of three pairs of messages, totaling six packets. The first pair exchanges Security Association proposals, the second exchanges Diffie-Hellman public keys and nonces, and the final pair authenticates the peers and exchanges identities securely.

Concept tested: IPSec IKEv1 Main Mode packet exchange

Source: https://www.cisco.com/c/en/us/support/docs/ip/ipsec/13840-ipsec-ike.html

Topics

#IPSec#IKEv1#Main Mode#Phase 1 Negotiation

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