Several NAS clients behind NAT

Hi! I'm running a FreeRADIUS server that's not directly accessible from the NAS clients, but they're all originating from the same source ip. Is this setup at all possible, or do I need to do some dirty hacks with NAT magic to accomplish this? When running with the same ip address (nasname), I get: "Failed to add duplicate client <shortname>". So I guess I have to do something to work around this? -- Marius