You may be on a ADSL and need to make sure that your modem is always operational. So the modem-connection needs to be tested and reset when the connection is down. There may be perfect systems out there to do this. I use a script to test and reset. The first one is a simple bash script performing a reset over the modem telnet, the second one is a python script that tests for a working concection and resets when needed.
Add to cron to test as often as you like, e.g. every 6 hours
#!/bin/bash
USERNAME='bigboss'
PDW='verysecret'
MODEM='10.1.1.1'
( echo open $MODEM
sleep 3
echo -e "$USERNAME\r\n"
sleep 3
echo -e "$PDW\r\n"
sleep 3
echo -e "system reboot\r\n"
sleep 5) | telnet
#!/usr/bin/env python
# This script will ping to google.nl and if network is
# unreachable it will connect to the modem and reboot it.
# Original author: Boris Bolgradov
# Modified: FvW 20120505
import os
import commands
import pexpect
def adsl_reboot():
p = pexpect.spawn('telnet 10.1.1.1')
p.expect('Username : ')
p.sendline('bigboss\r\n') # Sending Username.
p.expect('Password : ')
p.sendline('verysecret\r\n') # Sending Password.
p.expect('=>') #check you user manual
p.sendline('system reboot\r\n') # Sending command to the shell.
result = commands.getoutput("ping -c 1 google.nl")
if ((result.find("Unreachable") > -1) or (result.find("unknown") > -1)) :
print 'Not connected! - Rebooting the modem.'
adsl_reboot()
#else:
# print 'Connected'
email: f_vanwestrenen @ umantec . nl