“Authentication-wise, both versions support PSK and certificate signature . Although only IKEv1 supports XAuth ...”

“Now, you will learn about the Authentication section in phase 1 configuration:

• Method: FortiGate supports two authentication methods: Pre-shared Key and Signature. When you select Pre-shared Key, you must configure both peers with the same pre-shared key. When you select Signature, phase 1 authentication is based on digital certificate signatures.”

“The purpose of phase 1 is to authenticate peers and set up a secure channel... To authenticate each other, the peers use two methods: pre-shared key or digital signature . You can also enable an additional authentication method, XAuth, to enhance authentication. ”

“A common use of the IPsec wizard is for configuring a remote access VPN for FortiClient users. The wizard enables IKE mode config, XAuth , and other appropriate settings for FortiClient users.”

Technical Deep Dive:

The correct answers are C and D .

D is correct because FortiGate supports the two primary IKEv1 authentication methods: pre-shared key and certificate signature . That is explicitly stated in the study guide.

C is also correct because FortiGate supports XAuth with IKEv1 as an additional authentication mechanism. In practice, XAuth is used to request extra user credentials such as a username and password , especially in remote-access VPN deployments such as FortiClient.

Why the other options are incorrect:

A is incorrect because when using Signature , certificate-based authentication is in use. The study guide states that digital signature validation depends on the relevant certificates and CA trust chain being present. It is not a certificate-free method.

B is incorrect because “fewer packets are exchanged” is a characteristic of aggressive mode , not XAuth. XAuth enhances authentication; it is not the feature that makes IKE negotiation faster.

So the two supported IKEv1 authentication features are:

Extended authentication (XAuth) to request the remote peer to provide a username and password

Pre-shared key and certificate signature as authentication methods