How many packets are used in IKEv1 Phase 1 Main Mode exchange?

The correct answer isA. IKEv1 Phase 1 Main Mode usessix packets. Check Point’s R82 Site-to-Site VPN guide states that Main Mode is the default IKEv1 Phase 1 mode and that the Security Gateway performs the IKE negotiation with six packets. Main Mode is preferred over Aggressive Mode because part of the exchange becomes encrypted once both peers know the shared Diffie-Hellman key, and it is less susceptible to denial-of-service conditions than Aggressive Mode. Option D is wrong because three packets correspond to IKEv1 Aggressive Mode, not Main Mode. Option B and Option C are not valid packet counts for the standard IKEv1 Main Mode exchange. For CCSE exam precision, memorize the simple mapping:IKEv1 Main Mode = 6 packets; IKEv1 Aggressive Mode = 3 packets. This is one of the standard Check Point VPN mechanics questions and appears frequently because it tests whether the candidate can distinguish Main Mode from Aggressive Mode without confusing them with IKEv2 exchanges. Reference topic:IKE Phase I Modes.

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