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This document describes the installation of a pptp-Client for a xDSL-connection using an Ethernet-modem.
With the
separation of Telecom-Access-Provider (having a monopoly over the
cables in a certain area) and Internet-Service-Provider (ISP,
offering connection to the internet, providing mailboxes and
webspace), the Telecom-Access-Provider needs an instrument to
identify to which ISP the TCP/IP-packets should be forwarded and to
wrap the throughpassing packets in a way that they retain their
information.
To achieve these goals, the TCP/IP-packets are
transported using the pptp.
The
setup is specific for ADSL of Telekom Austria - but might work with
other Telekoms using pptp.
It was tested with an
Alcatel-SpeedTouch-510 modem. (These modems
are now sold by Thomson).
Credits:In
general thanks to Manuel Capellari, whose document 'ADSL unter Linux'
(http://www.gnustuff.com/pub/doc/adsl-howto/adsl-howto.html
- in german) was a valuable guideline on the way to my
highspeed-internet-connection.
Additional hints I derived from
Heimo
Schöns HOWTO (http://howto.htlw16.ac.at/at-highspeed-howto.html
- in german) particularly the hint of Martin Großhauser how to
start / restart the connection using crontab.
Operating-system
installed ;-).
The operating-system must be a RedHat**-Linux
9 or higher (Linux
Fedora Core 3)
Firewall
including IP-forwarding and Native-Address-Translation installed
(see Linux** -
Firewall and Masquerading).
This is a prerequisite only if
installing the pptp-Client on a router.
Logged on as user root.
ppp-package
has a version of 2.4.2 or higher.
For verification and upgrade
please see Linux** - Upgrade of
the ppp package to version 2.4.2.
Installation-instruction:The
configuration of the NICs is highly dependant on the manufacturer and
the type of the NIC.
If there are 2 NICs installed (1 for the
internal network, 1 for the connection to an ISP over ADSL, DSL or
cable-modem), then it is strongly recommended to use different types
of NIC. This simplifies the identification which NIC should be
connected to which cable.
Newer
network-interface-cards (NIC) are detected during the
standard-installation.
If this is so, you will already find the
configuration (symbolic i/o and driver) in the file
/etc/modules.conf;
an example is shown here:
alias
eth0 3c59x
alias eth1 ne
If other lines are already existing in this file they must not be deleted.
If the card was not
detected during the installation, the bold line might be missing.
In
this case, driver and - if the card has not a plug-and-play
capability - the i/o-parameters must be assigned manually by editing
the file
/etc/modules.conf.
A detailed description for a lot of NICs can be found in the
Linux
Ethernet-HOWTO.
Special procedure for notebooks (pc-card).
NIC-function is available
after starting pc-card-services.
For this reason, NICs can
not be detected during installation but are available after a restart
of Linux.
To identify the adaptors (if there are more than 1
installed), the configuration needs the io-ports of the individual
adaptors. This information is written into the log during startup and
can be viewed (after logon as 'root') with the command
dmesg
| tail
which shows a result
containing lines similar like these:
eth0:
NE2000 Compatible: io 0x300, irq 3, hw_addr
00:E0:98:33:72:48
eth1: NE2000 Compatible: io 0x340, irq 5,
hw_addr 00:E0:98:78:D8:B8
The underlined values are the identifiers of the pc-cards and can be used to assign TCP/IP-addresses.
During the installation of the operating-system for the router it was advised not to enter parameters for the second network-interface-card (NIC). So the parameters have to be set manually by editing the file /etc/sysconfig/network-scripts/ifcfg-eth1 :
DEVICE=eth1
BOOTPROTO=static
IPADDR=10.0.0.140
NETMASK=255.0.0.0
ONBOOT=yes
If the configuration is as planned can be verified after a restart with the command:
ifconfig eth1
The
most current version can be downloaded as a rpm-file from the
following internet-site:
http://switch.dl.sourceforge.net/sourceforge/pptpclient/pptp-linux-1.5.0-1.i386.rpm
:
Download
the file to a directory of your choice (furtheron referred as
download_directory).
After
the download is complete, start the installation using the
RedHat-Packet-Manager by issuing the following command:
rpm
-Uvh /download_directory/pptp-linux-1.5.0-1.i386.rpm
Store the user-id and password
for the connection to the ISP:The
Internet-Service-Provider usually provides an user-id and a password
to identify individual clients.
During the dial-in-procedure the
ISP performs an identification and requests user-id and password.
There
are 2 different authentification-protocols (PAP and CHAP); if you are
not sure what protocol the ISP uses it is recommended to store
user-id and password for both protocols.
For
the PAP-authentification edit the file /etc/ppp/pap-secrets
and add the bold printed line.
Instead of the
italics printed values in the examples, enter user-id and password
provided by the ISP:
# Secrets for
authentication using PAP
# client server secret IP
adresses
user-id * password
For
the CHAP-authentification edit the file /etc/ppp/chap-secrets
and add the bold printed line.
Instead of the
italics printed values in the examples, enter user-id and password
provided by the ISP:
# Secrets for
authentication using PAP
# client server secret IP
adresses
user-id * password
Edit the
configuration file for the pptp-Client:The
pptp-client is controlled - like the ppp-dialer
- by the parameters in the file /etc/ppp/options
;
the bold printed values have to be modified according to your needs:
#
# Debug-option;
recommended for the trial-phase.
# Can be commented out if the
pptp-connection is proven as stable
debug##
#
The computer on Internet-Service-Provider (ISP) must provide a
temporary TCP/IP-address
noipdefault#
#
The computer on Internet-Service-Provider (ISP) does not have to
identify itself
# against the computer dialing-in
noauth
#
This connection is the default-router from the internal network to
the ISP.
defaultroute#
#
User, for whom the password is read out of the file 'pap-secrets' or
'chap-secrets'
user “user-id“
#
#
End of file
Start
/ stop / restart script for the pptp-ClientTo
start or to restart the pptp-Client, I found a suitable script in
Heimo Schöns HOWTO. It is stored in the file
/etc/rc.d/adsl
:
#!/bin/bash
#
#
/etc/rc.d/adsl
#
# Script to start / stop /restart the
ADSL-modem for a pptp-connection
#
# Tested with RedHat-Linux
9.
# October 2004
# Kurt Gstoettner
#
# This script is
based on examples published by
# Sebasian C.B. Sauer
<scbATenemyDOTorg>
# Nicolas Croiset
<ncroisetATvdldiffussionDOTcom>
# Philippe Jouguet
<pjouguetATvdldiffusionDOTcom>
#
# Permission to copy is
granted provided that credit is given to all
# documentation you
used to understand these procedures
#
# No warranty is implied.
Use at your own risk !!
#
start() {
# start the adsl-Client
on the ADSL-modem with TCP/IP-address 10.0.0.138
/usr/sbin/pptp
10.0.0.138
# touch the processes to lock them
touch
/var/lock/subsys/pptp
touch /var/lock/subsys/pppd
echo -n
"adsl:procedure start()."
# Wait 15 seconds to allow the
pptp-client to get the TCP/IP-address
# from the
Internet-Service-Provider.
# Start the firewall thereafter.
sleep
15s
#
Start the firewall and the ip-forwarding if this script runs on the
router.
# Otherwise comment out the next line.
firewall
return
1
}
#
stop() {
echo -n "Shutting down PPTP tunnel.
"
# Kill the processes for the ppp-protocol
(Point-to-Point-Protocol)
# and the
Point-to-Point-Tunneling-Protocol
# to free the devices for a new
start.
killall /usr/sbin/pppd
killall /usr/sbin/pptp
rm -f
/var/loc/subsys/pptp
echo -n "adsl:procedure stop()."
return
1
}
#
firewall()
{
# Run the script to configure the
firewall
/etc/rc.d/rc.firewall-iptables
return 1
}
#
#
case "$1" in
start)
# check if the
ADSL-modem is operational
if ping -c 1 -w 1 10.0.0.138 >
/dev/null
then
echo -n "Starting PPTP/PPP tunnel.
"
start
else
# maybe ADSL-modem is just syncing; wait
45 seconds
echo -n "Waiting for ADSL-modem, start delayed
..."
sleep 45s
start
fi
;;
#
stop)
stop
;;
#
restart)
# stop, wait 15 seconds to make
sure all asynchronus tasks are completet, start
stop
sleep
15s
start
;;
#
*)
echo -n "Usage: adsl
{start|stop|restart}"
exit 1
;;
esac
exit $?
Setting the
access-rights for an automated startupAs
a prerequisite for automated startup or restart the access-rights of
the script must be set as follows:
chmod
4711 /etc/rc.d/adsl
Automatic start /
restart of the pptp-client using crontabAs
mentioned in the credits, Martin Großhauser developed a pretty
smart method to start or restart the pptp-client.
Every 5 minutes
a ping is issued to a known TCP/IP-address on the internet. If this
ping is without an answer, the Start
/stop / restart script is run with the parameter
'restart'.
All this is achieved by simply adding one line to
the
file /etc/crontab
.
As my connection is with the Telekom Austria, I ping their
primary nameserver.
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/
#
#
run-parts01 * * * * root run-parts /etc/cron.hourly02
4 * * * root run-parts /etc/cron.daily
22
4 * * 0 root
run-parts /etc/cron.weekly
42 4
1 * * root run-parts /etc/cron.monthly# Restart the pptp-Client if no
response.0,5,10,15,20,25,30,35,40,45,50,55
* * * * root ping -c 1 195.3.96.67 || /etc/rc.d/adsl restart
The
file can only be edited with access-rights as 'root'.
On
a workstation set the gateway and ping a known address; e.g. the
Domain-Name-Server of the Internet-Service-Provider
ping
195.3.96.67