Speedtouch 510 setup with Linux

December 22, 2007

linux

You have gotten your adsl modem (in my case a speedtouch 510) and you want to use linux to do the routing and firewalling stuff. Mainly because the 510 is a very brain dead modem, which mangles too long DNS packets, can’t do IPv6, etc, etc.

I’ve seen a lot of pages about SIP_SPOOF and DHCP_SPOOF (for details I refer to google). People remarked that those things worked, but are a hack. If you go down this rat hole, use SIP_SPOOF instead of DHCP_SPOOF, because that is a lesser hack IMO.

Also I have KPN ADSL (Netherlands), you might have more luck if you use ADSL from bbeyond. If I knew then what I know now, I hadn’t taken KPN ADSL…

Anyhow, I couldn’t get either of these hacks to work at my place, so I needed something else. This page tells you what I did; it boils down to using the modem as some kind of bridge and do the actual calling from your linux box. You actually get a ppp0 device which is your Internet connection. Just as in the go’old times ;-)

You need to setup your local network so that you can communicate with your modem. This means having a 10.0.0.0/8 address on your ethernet that is connected to your modem.

modem side

It is assumed you can reach your modem on 10.0.0.138 and you have a browser handy.

Put the CD from KPN in your computer and find a file called PPTP.INI on it. Upload this configuration file to your modem. You may need to rename the file to PPTP.ini. Next configure your modem, disable DNS, DHCP, i.e. all the br0ken stuff. Your modem now only bridges between the local ethernet and the adsl connection.

Note: I couldn’t get the bridging going be using easy-setup (->Bridging) in the modem’s configuration, I really had to upload this PPTP.INI file to the modem.

linux side

Download pptp-linux, it’s in Debian/Ubuntu. Configure it to make it work. Examples of configuration can be found on the website from pptp-linux.

Make it work at boot time - the Debian way

This was a bit difficult, but I got it working in the end. In /etc/ppp/peers create a file with a name for your connection. I called mine xs4all, in there put:

pty "pptp 10.0.0.138 --nolaunchpppd"
user `yourusername@axs4all'
lcp-echo-interval 10
lcp-echo-failure 3
defaultroute
persist

Also be sure to update the /etc/ppp/options and /etc/ppp/pap-secrets according to pptp-linux’s documentation.

And in /etc/network/interfaces add the following:

# ADSL ppp config
iface xs4all inet ppp
    provider xs4all

where provider xs4all must match the name of the file under /etc/ppp/peers. Don’t forget auto xs4all somewhere in that file and you’re set to go.

trying it out

Do a pptp 10.0.0.138, this should yield (after one or two seconds) a ppp0 interface with your ip address. After this I was able to ping hosts on the Internet. It worked :-):
ppp0      Link encap:Point-to-Point Protocol
          inet addr:xx.xx.17.126  P-t-P:xx.xx.250.2  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:1036930 errors:0 dropped:0 overruns:0 frame:0
          TX packets:639014 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:1167757439 (1.0 GiB)  TX bytes:50856576 (48.5 MiB)

Kill your pppd daemon and try the command pon xs4all, this should now also work. Kill the connection with poff xs4all. If this works the stuff from /etc/network/interfaces should also work. Try ifup xs4all, if that works the interface should also come up during boot.

the future and beyond

Next I need to reconfigure my firewall and setup the (new) internal network, but that is all trivial.

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