===== Step 4: Option 2: Get a Service VM Running as a vRouter (SLAAC) =====

# Current network setup for IPv6 router VM on local virtualbox setup\\
# /etc/sysconfig/network-scripts/ifcfg-enp0s3\\
# Network interface enp0s3 is IPv4 for public internet access\\
TYPE="Ethernet"\\
BOOTPROTO="dhcp"\\
DEFROUTE="yes"\\
PEERDNS="yes"\\
PEERROUTES="yes"\\
IPV4_FAILURE_FATAL="no"\\
IPV6INIT="yes"\\
IPV6_AUTOCONF="yes"\\
IPV6_DEFROUTE="yes"\\
IPV6_PEERDNS="yes"\\
IPV6_PEERROUTES="yes"\\
IPV6_FAILURE_FATAL="no"\\
NAME="enp0s3"\\
UUID="32bad876-680a-4f78-a364-726eae21bfcf"\\
DEVICE="enp0s3"\\
ONBOOT="yes"\\

# /etc/sysconfig/network-scripts/ifcfg-enp0s8\\
# Network interface enp0s8 is IPv6 internal interface to provide IPv6 to internal hosts\\
BOOTPROTO=static\\
IPV6INIT=yes\\
IPV6ADDR="2001:db8:0:2::1/64"\\
NAME=enp0s8\\
UUID=e931a806-2f76-425d-b035-d37813b81df5\\
DEVICE=enp0s8\\
ONBOOT=yes\\
NM_CONTROLLED=no\\

# Disable NetworkManager\\
systemctl disable NetworkManager\\

# Install dhcp.x86_64, dhcp-common.x86_64, radvd.x86_64 if not already installed\\
yum install dhcp-common\\
yum install dhcp\\
yum install radvd\\

# /etc/sysctl.conf Set sysctl to enable IPv6 forwarding\\
net.ipv6.conf.all.forwarding=1\\
net.ipv6.conf.enp0s3.accept_ra=2\\
net.ipv6.conf.enp0s3.accept_ra_defrtr=1\\
net.ipv6.conf.enp0s3.router_solicitations=1\\

# /etc/radvd.conf\\
interface enp0s8\\
{\\
# This is the primary "on switch" for RADVD
    AdvSendAdvert on;     
#\\
# These settings determine how often advertisements will be sent every X-Y.\\
# X and Y are in seconds. With these settings you will be sending a advert every 60 seconds\\
#\\

    MinRtrAdvInterval 60;
    MaxRtrAdvInterval 180;

#\\
# Disable Mobile IPv6 support\\
#\\
    AdvHomeAgentFlag off;

# Here we set our managed flags\\

    AdvManagedFlag on;
    AdvOtherConfigFlag on;

#\\
# Enter our IPv6 prefix and CIDR\\
#\\
    prefix 2001:db8:0:2::/64
    {
        AdvOnLink on;
        ### On link tells the host that the default router is on the same "link" as it is
        AdvAutonomous on;
        AdvRouterAddr off;
    };

};\\

# Enable radvd service\\
systemctl enable radvd\\

# In /etc/sysconfig/network add\\
IPV6FORWARDING=yes\\

===== Step 4: Option 2: Get a Service VM Running as a vRouter (DHCPv6 Stateful Server) =====

# Current network setup for IPv6 router VM on local virtualbox setup\\
# /etc/sysconfig/network-scripts/ifcfg-enp0s3\\
# Network interface enp0s3 is IPv4 for public internet access\\
TYPE="Ethernet"\\
BOOTPROTO="dhcp"\\
DEFROUTE="yes"\\
PEERDNS="yes"\\
PEERROUTES="yes"\\
IPV4_FAILURE_FATAL="no"\\
IPV6INIT="yes"\\
IPV6_AUTOCONF="yes"\\
IPV6_DEFROUTE="yes"\\
IPV6_PEERDNS="yes"\\
IPV6_PEERROUTES="yes"\\
IPV6_FAILURE_FATAL="no"\\
NAME="enp0s3"\\
UUID="32bad876-680a-4f78-a364-726eae21bfcf"\\
DEVICE="enp0s3"\\
ONBOOT="yes"\\

# /etc/sysconfig/network-scripts/ifcfg-enp0s8\\
# Network interface enp0s8 is IPv6 internal interface to provide IPv6 to internal hosts\\
BOOTPROTO=static\\
IPV6INIT=yes\\
IPV6ADDR="2001:db8:0:2::1/64"\\
NAME=enp0s8\\
UUID=e931a806-2f76-425d-b035-d37813b81df5\\
DEVICE=enp0s8\\
ONBOOT=yes\\
NM_CONTROLLED=no\\

# Disable NetworkManager\\
systemctl disable NetworkManager\\

# Install dhcp.x86_64, dhcp-common.x86_64, radvd.x86_64 if not already installed\\
yum install dhcp-common\\
yum install dhcp\\
yum install radvd\\

# /etc/sysctl.conf Set sysctl to enable IPv6 forwarding\\
net.ipv6.conf.all.forwarding=1\\
net.ipv6.conf.enp0s3.accept_ra=2\\
net.ipv6.conf.enp0s3.accept_ra_defrtr=1\\
net.ipv6.conf.enp0s3.router_solicitations=1\\

# /etc/dhcp/dhcpd6.conf\\
# DHCP for IPv6 Server Configuration file.

# Enable RFC 5007 support (same than for DHCPv4)\\
    allow leasequery;

# IPv6 address valid lifetime\\
#  (at the end the address is no longer usable by the client)\\
#  (set to 30 days, the usual IPv6 default)\\
    default-lease-time 2592000;

# IPv6 address preferred lifetime\\
#  (at the end the address is deprecated, i.e., the client should use\\
#   other addresses for new connections)\\
#  (set to 7 days, the  usual IPv6 default)\\
    preferred-lifetime 604800;

# T1, the delay before Renew\\
#  (default is 1/2 preferred lifetime)\\
#  (set to 1 hour)\\
    option dhcp-renewal-time 3600;

# T2, the delay before Rebind (if Renews failed)\\
#  (default is 3/4 preferred lifetime)\\
#  (set to 2 hours)\\
    option dhcp-rebinding-time 7200;

# The path of the lease file\\
    dhcpv6-lease-file-name "/var/lib/dhcpd/dhcpd6.leases";

# Set preference to 255 (maximum) in order to avoid waiting for\\
# additional servers when there is only one\\
    option dhcp6.preference 255;

# Server side command to enable rapid-commit (2 packet exchange)\\
    option dhcp6.rapid-commit;

# The delay before information-request refresh\\
#  (minimum is 10 minutes, maximum one day, default is to not refresh)\\
#  (set to 6 hours)\\
    option dhcp6.info-refresh-time 21600;

# Set this to `interim' when doing ddns updates\\
    ddns-update-style interim;

    subnet6 2001:db8:0:2::/64 {
        option dhcp6.name-servers 2001:db8:0:2::1;
        option dhcp6.domain-search "opnfv.local";
        ddns-hostname = concat(binary-to-ascii(10, 8, "-", leased-address), ".wired");
        ddns-domainname = "opnfv.local";
        # Our address range 1000 through 1fff
        range6 2001:db8:0:2::1000 2001:db8:0:2::1fff;
    }


# In /etc/sysconfig/network add\\
IPV6FORWARDING=yes\\

For reference "How to set up RADVd DHCPv6 and DNS on CentOS 6"  refer
[[http://www.percula.info/archives/196]]