In order to check that the stack works, execute #ping6 ::1. If the result is the following (or similar):

PING ::1(::1) with 56 data bytes

64 bytes from ::1: icmp_seq=1 ttl=64 time=0.046 ms
64 bytes from ::1: icmp_seq=2 ttl=64 time=0.016 ms
64 bytes from ::1: icmp_seq=3 ttl=64 time=0.013 ms
64 bytes from ::1: icmp_seq=4 ttl=64 time=0.012 ms
64 bytes from ::1: icmp_seq=5 ttl=64 time=0.009 ms

It means that you already have installed, correctly, the IPv6 stack in your machine.

In order to check that the kernel kernel supports IPv6, the following entrance must exists:
/proc/net/if_inet6

If it does not exist, you can try to load the IPv6 module with:
modprobe ipv6

For loading, automatically, the IPv6 module when it is required, you should add to etc/modules.conf file, the following code line:

alias net-pf-10 ipv6
alias sit0 ipv6
alias sit1 ipv6
alias tun6to4 ipv6

To disable automatic loading you should use alias net-pf-10 off

To configure IPv6, you need some of the following tools:

net-tools packet: Using ifconfig, route. All present versions supports IPv6 extensions.

iproute packet: The programa /sbin/ip must exist, since this program is the previous packet extension, all versions have IPv6 support incorporated.