How can I assign multiple IPv6 addresses with DHCPv6 to a single interface?
I haven't tried this, but here's what I think would work:
Use brctl addbr to create a virtual switch. Create two virtual interfaces (with commands like ip tuntap add mode tap). Then add both tap interfaces and your physical interface to the bridge (e.g. brctl addif tap0). Now you have two interfaces on which to run dhcp clients.