import re


def valid_mac(mac=None):
    """Validates Ethernet MAC Address

    :param: mac address to validate
    :type: str
    :return: denotes true if MAC proper format else flase
    :rtype: bool
    """
    if mac is None or mac.strip() == "":
        return False
    mac = mac.strip()
    return re.match("^([0-9A-Fa-f]{2}[:.-]?){5}([0-9A-Fa-f]{2})$", mac)