class NetUtils {

    public static String generateMacOnIncrease(final String baseMac, final long l) {
        long mac = mac2Long(baseMac);
        if (l > 0xFFFFl) {
            return null;
        }
        mac = mac + (l << 24);
        mac = mac & 0x06FFFFFFFFFFl;
        return long2Mac(mac);
    }

}