For an ESXi host to be able to access iSCSI targets, it needs to be configured with an iSCSI initiator (adapter). For cases where you do not have hardware iSCSI initiators available, VMkernel has a software iSCSI adapter built into it; however, it is not enabled by default.
Adding the software iSCSI adapter
Getting ready
The software iSCSI adapter will use the VMkernel network stack to establish sessions with the iSCSI targets. Hence, by default, it will use the management network's VMkernel interface (vmk0). It is recommended that you create a different VMkernel interface for iSCSI. This will become essential when the management network is in a different subnet than the IP storage network.