change_gateway_centos.sh

change_gateway_centos.sh

#!/bin/bash

LOG_FILE="/tmp/user_script_log"

logit()
{
    echo "[${USER}][`date`] - ${*}" >> ${LOG_FILE}
}

logit "Start to user script to update default gw"

IP=$(/sbin/ip route | awk '/default/ { print $3 }')
# .4 address is gw on netscaler
GATEWAY_IP=`echo $IP | awk -F '.' '{print $1"."$2"."$3"."4}'`
logit "original gw is $IP"
logit "new gw is $GATEWAY_IP"

# Check if gateway ip start from 10.X.Y.Z
start=$(echo "$GATEWAY_IP"|  awk -F '.' '{print $1}')
if [ $start == '10' ]
then
    logit "$GATEWAY_IP is 10.X.Y.Z internal IP"
else
    logit "$GATEWAY_IP is not 10.X.Y.Z internal IP"
    exit
fi

ping -q -c3 $GATEWAY_IP > /dev/null
if [ $? -eq 0 ]
then
    logit "ping $GATEWAY_IP success"
else
    logit "ping $GATEWAY_IP error"
    exit
fi

if [ "$GATEWAY_IP" ]
then
    ip route replace default via $GATEWAY_IP
    grep -q "GATEWAY=$GATEWAY_IP" /etc/sysconfig/network || echo "GATEWAY=$GATEWAY_IP" >> /etc/sysconfig/network
    logit "Updated /etc/sysconfig/network and default route"
fi