Client isolation while roaming across multiple AP's (using same IP)

[Gruntruck]

@CuteRoute

To isolate clients of different APs within your guest VLAN, set up your central router such that traffic within the VLAN's subnet is disallowed. That's the whole trick.

Yes, that is exactly what I would like to do. But how do I do that in practice and still retain one DHCP server/IP range for all four VLAN's?

I will have VLAN5,VLAN6,VLAN7,VLAN8. All those VLAN's must have same subnet and device that for example receives IP 192.168.5.155 must be able to "roam" from VLAN5 to VLAN6 and still retain that IP.