Which of the following CHAP Authentication mechanisms is available when using Software iSCSI,
but not Hardware iSCSI?

A.
Per-Subnet CHAP

B.
One-way CHAP

C.
Per-Target CHAP

D.
Mutual CHAP

Explanation:
ESXi supports one-way CHAP for all types of iSCSI initiators, and mutual CHAP for software and dependent hardware iSCSI.
One-way CHAP
In one-way CHAP authentication, also called unidirectional, the target authenticates the initiator, but the initiator does not authenticate the target.

Mutual CHAP
In mutual CHAP authentication, also called bidirectional, an additional level of security enables the initiator to authenticate the target. VMware supports this method for software and dependent hardware iSCSI adapters only.