import re


def convert_macaddr_format_to_colon(macaddr: str) -> str:
    """Convert NXOS/EOS . macaddr form to standard : format, lowecase

    :param macaddr: str, the macaddr string to convert
    :returns: the converted macaddr string or all 0s string if arg not str
    :rtype: str

    """
    if isinstance(macaddr, str):
        if re.match(r'[0-9a-zA-Z]{4}.[0-9a-zA-Z]{4}.[0-9a-zA-Z]{4}', macaddr):
            return (':'.join([f'{x[:2]}:{x[2:]}'
                              for x in macaddr.split('.')])).lower()
        else:
            return macaddr.lower()

    return('00:00:00:00:00:00')