It is simple and straight forward to enable IPv6 on KVM guests
Configure the host machine with IPv6 Address on the bridge interface
cat ifcfg-br0
IPV6INIT=yes
IPV6ADDR=xxxx.xx::10
IPV6_DEFAULTGW=xxxx.xx::1
IPV6_AUTOCONF=no
Configure the interface on virutal machines with ipv6 address
cat ifcfg-eth0
IPV6INIT=yes
IPV6ADDR=xxxx.xx::11
IPV6_DEFAULTGW=xxxx.xx::1
IPV6_AUTOCONF=no
Add the the necessary firewall rules to ip6tables on the host machine
-A FORWARD -m physdev –physdev-is-bridged -j ACCEPT.
./arun