If your service profile is built from a self-updating service profile template, make sure you have both options in the boot policy in the template and the service profile will automatically be updated. If you want to change just a single service profile that is associated with a template, you need to first disassociate the service profile from the template and then modify the options in the service profile's boot policy.
A boot policy could have both SAN and network boot options. Then at boot time, you would F6 the machine and select the PXE boot if the SAN boot was the default.
But I'm not sure if that is what you are asking. Could you please provide a little bit more information about what you are trying to accomplish?
