John,

When you say that they all get the same address, you probably mean that the loopback interfaces have IPv6 addresses part of the FE80::/10. These are link local addresses as shown in the following document:

http://www.iana.org/assignments/ipv6-address-space

These addresses are assigned automatically to each interface and serve for communication between IPv6 devices on a local link.

As for ::1/128, you can't configure it on any interface and you should get the following message if you try:

Router(config-if)#ipv6 address ::1/128

%Loopback0: Error: ::1/128 is invalid

One more thing, you can't configure autoconfig on the loopback as this command assumes that there is another device on the subnet from which you can get autoconfiguration information.

Your best option would be to configure valid ipv6 addresses statically on the loopback interface(s) as follow:

for instance

int lo0

ipv6 address 2001:db8;12ff::1/128

or

ipv6 address 2001:db8;12ff::/64 eui-64

Regards