Mikrotik Carrier-grade NAT (Cgnat) Algorithms

mikrotik_cgnat.py

import ipaddress

def calculate_ports(public_ip: str, port_interval: int, port_start: int, port_end: int) -> list:
    """
    Calculates a list of port ranges based on the provided parameters.

    Args:
        public_ip (str): The public IP address.
        port_interval (int): The interval between port ranges.
        port_start (int): The starting port.
        port_end (int): The ending port.

    Returns:
        list: A list of dictionaries representing port ranges.
    """
    if port_start > port_end:
        raise ValueError("Start port cannot be greater than End port")

    if not ipaddress.ip_address(public_ip).is_private:
        if port_end > 65535:
            raise ValueError("End port cannot be greater than 65535.")
        if port_start <= 0 or port_start >= 65535:
            raise ValueError("Start port must be between 1 and 65534.")
        if port_interval <= 0 or port_interval >= 65535:
            raise ValueError("Port interval must be between 1 and 65534.")

        port_ranges = []
        current_port = port_start
        customer_counter = 1

        while current_port < port_end:
            end_port = min(current_port + port_interval, port_end)
            port_range = {
                "PublicIp": public_ip,
                "StartPort": current_port,
                "EndPort": end_port,
                "CustomerCounter": customer_counter
            }
            port_ranges.append(port_range)

            current_port = end_port + 1
            customer_counter += 1

        return port_ranges
    else:
        raise ValueError("Entered IP is a private IP")

# Example usage:
if __name__ == "__main__":
    result = calculate_ports("171.161.1.2", 1000, 1000, 10000)
    for x in result:
        print(x)

Output ->
{'PublicIp': '171.161.1.2', 'Startport': 2001, 'EndPort': 3000, 'CustomerCounter': 1}
{'PublicIp': '171.161.1.2', 'Startport': 3002, 'EndPort': 4001, 'CustomerCounter': 2}
{'PublicIp': '171.161.1.2', 'Startport': 4003, 'EndPort': 5002, 'CustomerCounter': 3}
{'PublicIp': '171.161.1.2', 'Startport': 5004, 'EndPort': 6003, 'CustomerCounter': 4}
{'PublicIp': '171.161.1.2', 'Startport': 6005, 'EndPort': 7004, 'CustomerCounter': 5}
{'PublicIp': '171.161.1.2', 'Startport': 7006, 'EndPort': 8005, 'CustomerCounter': 6}
{'PublicIp': '171.161.1.2', 'Startport': 8007, 'EndPort': 9006, 'CustomerCounter': 7}