gwtest.sh

#!/bin/sh

# Master ISP
isp1_ip="85.143.163.113"

# Backup ISP
isp2_ip="91.220.11.1"

is_set()
{
    ip="$1"
    gw=`/usr/bin/netstat -rn -4 | /usr/bin/grep 'default' | /usr/bin/awk '{print $2}'`
    test $gw = $ip
}

set_gw()
{
    ip="$1"
    /sbin/route change default $ip
}

if /sbin/ping -c 10 -n -q $isp1_ip > /dev/null 2>&1
then
    is_set $isp1_ip || set_gw $isp1_ip
else
    is_set $isp2_ip || set_gw $isp2_ip
fi