It looks like the esxcli command changes in ESXi 5.0 and later (it certainly has for some 5.1 boxes I just went to do this on). So you would need to do the below instead:
$esxcli.iscsi.networkportal.add($hba.Device, $false, "vmk1")
It looks like the esxcli command changes in ESXi 5.0 and later (it certainly has for some 5.1 boxes I just went to do this on). So you would need to do the below instead:
$esxcli.iscsi.networkportal.add($hba.Device, $false, "vmk1")