check prefix's route_family and if the address is
        IPv6 address, return IPv6 route_family and normalized IPv6 address.
        If the address is IPv4 address, return IPv4 route_family
        and the prefix itself.

def _check_rf_and_normalize(prefix):
        """ check prefix's route_family and if the address is
        IPv6 address, return IPv6 route_family and normalized IPv6 address.
        If the address is IPv4 address, return IPv4 route_family
        and the prefix itself.
        """
        addr, masklen = prefix.split('/')
        if ip.valid_ipv6(addr):
            # normalize IPv6 address
            ipv6_prefix = str(netaddr.IPAddress(addr)) + '/' + masklen
            return vrfs.VRF_RF_IPV6, ipv6_prefix
        else:
            return vrfs.VRF_RF_IPV4, prefix