Today I learned that with iSCSI you should set proper NICs to the iSCSI vmk’s.
Regarding http://www.vmware.com/pdf/vsphere4/r41/vsp_41_esxi_server_config.pdf Setting Up and Configuring Software iSCSI Adapter on page 91 you need to connect a physical NIC to the vmkernel interface which does the iSCSI traffic:
esxcli swiscsi nic add -n vmk2 -d vmhba37