Cannot add iSCSI lun via vCentre, only via host directly?

Hi,

I have installed vCentre 5 and for some reason I cannot add iSCSI LUNs to a host via vCentre.  The lun permissions are set correctly for the host, and if I connect directly to the host and go to add a LUN then it appears in the add storage wizard.

If I then go back and try and do the same operaiton via vCentre, it does not work. The LUN will only appear in the add storae wizard if directly connected to the host.

I am using HP P4300 SAN.

Is there something quite obvious I am missing here?

Thanks