Write a python script to transfer the network to another interface in case if one interface is down

 

Here’s an updated Python script that continuously monitors the network connection on a primary interface, and if it goes down, switches to a backup interface.

Python Script:

import os

import subprocess

import time

PRIMARY_INTERFACE = "eth0"  # Name of the primary network interface

SECONDARY_INTERFACE = "eth1"  # Name of the secondary network interface

PING_HOST = "8.8.8.8"  # Google's DNS server to check connectivity

CHECK_INTERVAL = 10  # Time interval between checks (in seconds)

def check_connectivity(interface):

    """Check if the given network interface has connectivity."""

    try:

        # Use ping to test connectivity on the specified interface

        result = subprocess.run(

            ["ping", "-I", interface, "-c", "1", PING_HOST],

            stdout=subprocess.PIPE, stderr=subprocess.PIPE

        )

        return result.returncode == 0

    except Exception as e:

        print(f"Error checking connectivity on {interface}: {e}")

        return False

def switch_interface(interface):

    """Bring the network interface up and make it the default route."""

    try:

        # Bring the interface up

        print(f"Bringing up interface {interface}")

        subprocess.run(["sudo", "ifconfig", interface, "up"], check=True)

        

        # Remove default route

        subprocess.run(["sudo", "ip", "route", "del", "default"], check=True)

        

        # Set the default route to the new interface

        subprocess.run(["sudo", "ip", "route", "add", "default", "dev", interface], check=True)

        

        print(f"Switched to {interface} successfully!")

    except Exception as e:

        print(f"Failed to switch to {interface}: {e}")

def main():

    using_secondary = False  # Flag to track the current active interface

    

    while True:

        # Check connectivity on the primary interface

        if check_connectivity(PRIMARY_INTERFACE):

            if using_secondary:

                print(f"Primary interface {PRIMARY_INTERFACE} is back. Switching back...")

                switch_interface(PRIMARY_INTERFACE)

                using_secondary = False

            else:

                print(f"Primary interface {PRIMARY_INTERFACE} is working fine.")

        else:

            print(f"Primary interface {PRIMARY_INTERFACE} is down.")

            

            # If primary is down, switch to secondary

            if not using_secondary:

                print(f"Switching to secondary interface {SECONDARY_INTERFACE}...")

                switch_interface(SECONDARY_INTERFACE)

                using_secondary = True

        

        # Wait for the next check

        time.sleep(CHECK_INTERVAL)

if __name__ == "__main__":

    main()

Key Points:

1. check_connectivity(interface): This function checks if the given network interface has internet connectivity by pinging a remote server (8.8.8.8).

2. switch_interface(interface): This function brings up the interface and changes the default route to that interface, ensuring the system routes all traffic through it.

3. main():

It continuously monitors the primary interface (eth0) every few seconds (as defined by CHECK_INTERVAL).

If the primary interface is down, it switches to the secondary interface (eth1), bringing it up and setting the route.

When the primary interface comes back online, it switches back to it.

Requirements:

The script uses sudo to bring interfaces up and modify routes.

Interfaces must be available (eth0, eth1) on your system.

You can adjust the network interfaces, ping target, and check interval as necessary for your environment.

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