def create_mpls_interface_desc(router_name, line_id, role):
    """
    pattern for interfaces with MPLS router connected:
    - <MPLS_PROVIDER><ROLE><MPLS><ROUTER_NAME><LINE_ID>
    """
    if role.lower() == "main":
        result = f'<MPLS_PROVIDER><MAIN><MPLS><{router_name}><{line_id}>'
        return result
    elif role.lower() == "backup":
        result = f'<MPLS_PROVIDER><BACKUP><MPLS><{router_name}><{line_id}>'
        return result