What is the maximum number of ipv6 addresses that can be assigned to one ipv6 interface?

Correct answer: An IPv6 interface is not limited in the number of addresses it can be assigned, althoughthere could be limitations based upon practicality.

Sample run, to give you an idea why that is:

R1#show ipv6 int

FastEthernet0/0 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::200:11FF:FE11:1111

No Virtual link-local address (es):

Global unicast address (es):

2001::1, subnet is 2001::/64

2001::2, subnet is 2001::/64

2001::3, subnet is 2001::/64

2001::4, subnet is 2001::/64

2001::5, subnet is 2001::/64

2001::6, subnet is 2001::/64

2001::7, subnet is 2001::/64

2001::8, subnet is 2001::/64

2001::9, subnet is 2001::/64

2001::10, subnet is 2001::/64

2001::11, subnet is 2001::/64

2001::12, subnet is 2001::/64

2001::13, subnet is 2001::/64

2001::14, subnet is 2001::/64

2001::15, subnet is 2001::/64

2001::16, subnet is 2001::/64

2001::17, subnet is 2001::/64

2001::18, subnet is 2001::/64

2001::19, subnet is 2001::/64

2001::20, subnet is 2001::/64

:

2001::200, subnet is 2001::/64