Connect to vCenter and click on ESXi host and go to configuration and networking.
Create vSwitch with VM Kernel port group and Map to a available VMNIC as shown in the below screen shot.
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Go to storage adapter and click on Add, Select Add Software iscsi adapter and click ok.
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Click on the properties tab and go to Network configuration tab,
Click on Add and Add the Switch that we have configured for ISCSI, as below.
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Now click on the ISCSI software adapter in the configuration tab and go to properties.
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Now click on the Dynamic Discovery tab, in the iSCSI Initiator Properties.
Click on Add and provide the details of iSCSI server and click ok, as below.
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We are done with the software iSCSI configuration for the ESXI 5.X host.
For testing the configured iSCSI setting, present a LUN from the array and go to configuration and click on storage view.
Click on add storage and select Disk/Lun type and click next you will see the LUN detected as below.
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So now your successfully configure Software iSCSI for the ESXi host.