Setup an IPv6 RA router

build and install the latest RA daemon

wget http://www.litech.org/radvd/dist/radvd-2.19.tar.gz
tar xzf radvd-2.19.tar.gz
cd radvd-2.19/
./configure
make
make install

enable forwarding on ALL INTERFACES

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

and check

cat /proc/sys/net/ipv6/conf/*/forwarding

setup the daemon to spit regularly on the internal network

vi /etc/radvd.conf

interface br0
{
    AdvSendAdvert on;
    # AdvLinkMTU 1280;
    MaxRtrAdvInterval 300;
    prefix 2001:bc8:204a:101::/64
    {
        AdvOnLink on;
        AdvAutonomous on;
    };
};

Ready to go (altogether)

enable at startup

vi /etc/rc.d/rc.inet1

    echo IPv6 SLAAC
    echo 2 > /proc/sys/net/ipv6/conf/xenbr0/accept_ra

    echo IPv6 forwarding
    echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

    echo IPv6
    /sbin/ifconfig br0 inet6 add x::1/64 up

    echo -n DUID...
    /sbin/dhclient -cf /etc/dhclient6.conf -6 -P xenbr0 -v && echo done || echo FAIL

    echo -n RADVD...
    /usr/local/sbin/radvd && echo done || echo FAIL
    echo

status

cat /proc/sys/net/ipv6/conf/*/forwarding
ifconfig
ps auxww | grep dhclient
ps auxfww | grep radvd

stop

ip addr del x::x/64 dev br0
/sbin/dhclient -x -pf /var/run/dhclient6.pid
pkill dhclient

Resources

Linux IPv6 Router Advertisement Daemon (radvd) http://www.litech.org/radvd/

IPv6 router guide https://wiki.gentoo.org/wiki/IPv6_router_guide

IPv6PrefixDelegation https://wiki.debian.org/IPv6PrefixDelegation

Linux box as an IPv6 router with SLAAC and DHCPv6-PD https://taczanowski.net/linux-box-as-an-ipv6-router-with-slaac-and-dhcpv6-pd/

Building an IPv6 router with GNU/Linux https://www.tomicki.net/ipv6.router.php