Ipv6 in Linux is supported since 1996. To test whether your specific linux system has ipv6 support use the following commands
if this produces an output like this
00000000000000000000000000000001 01 80 10 80 lo
fe80000000000000021320fffed711ee 02 40 20 80 eth0
then your kernel is ipv6 enabled.
If this command fails there is case that ipv6 module may not be loaded to kernel.
To test whether this module is loaded test
# modprobe ipv6
$ lsmod | grep ipv6
ipv6 240836 26
The output will be similar to this. If this fails you may have to compile kernel with ipv6 support.