Auto Change Default GW Ubuntu Script

README.md

#!/bin/bash

# List of gateways with corresponding interfaces
gateways=("192.168.100.1" "192.168.70.1" "192.168.80.1")
interfaces=("eth0" "eth1" "eth2")

# Function to check internet connectivity using a specific interface and gateway
check_gateway_connectivity() {
  interface=$1
  gateway=$2
  ping -I $interface -c 1 -W 1 $gateway > /dev/null 2>&1
  return $?
}

# Function to switch to a new gateway
switch_gateway() {
  new_gateway=$1
  new_interface=$2

  # Delete existing default route
  ip route del default

  # Update default route to the new gateway
  ip route replace default via $new_gateway dev $new_interface
  echo "Switched to gateway $new_gateway via interface $new_interface"
}

# Loop through gateways
for ((i=0; i<${#gateways[@]}; i++)); do
  gateway=${gateways[$i]}
  interface=${interfaces[$i]}

  # Check internet connectivity using the specific interface and gateway
  check_gateway_connectivity $interface $gateway

  if [ $? -eq 0 ]; then
    # If gateway is reachable, update default route
    switch_gateway $gateway $interface
    exit 0
  else
    echo "Gateway $gateway via interface $interface not reachable. Trying next..."
  fi
done

echo "No reachable gateway found."
exit 1