My First Linux Router: SuSE 5.3, Teles ISDN and the Blinking DSL Modem

C:\LINUX\HOMERO~1>type firstl~1.htm

My First Linux Router: SuSE 5.3, Teles ISDN and the Blinking DSL Modem

I wanted to start with Linux already earlier, but I did not. One reason was VFAT. I had too much DOS and Windows stuff on the disk and I did not want to make a big break just for trying Linux. Now SuSE 5.3 comes with kernel 2.0.35 and VFAT support is there in a way that feels usable for me, so now I finally do it.

Also I have enough curiosity to break my evenings with this, and enough little money to make bad hardware decisions and then keep them running because there is no budget for the nice version.

The machine for the router is a Cyrix Cx133. Not a fancy box. Right now it has 8 MB RAM and a 1.2 GB IDE disk. The case looks like every beige case looks. For a router it is enough. It boots. It stays on. It has one job. If I find cheap RAM later I will put it in, but first I want the basic thing working.

For ISDN I do not buy AVM because I simply cannot. Everybody says AVM is the good stuff and the drivers are nice and all is more easy. Fine. I buy a cheap Teles 16.3 PnP card. It is not the card of dreams, but it is my card and I can pay it. So the project now is not “what is best”, it is “what can be made to work with Teles and a bit stubbornness”.

At the same time there is already the whole T-DSL story from Telekom. This is maybe the funny part: I already subscribe to the DSL package together with T-Online, but the line is not switched yet. They give us the hardware. The DSL modem is there. The splitter is there. Everything is there. I can look at the modem and I can connect it and the LED is blinking and blinking and blinking. But there is no real DSL sync yet. It is like the future is already on the desk, only the exchange in the street does not care.

The good thing in this package is: I can already use ISDN with the same flatrate model through T-Online until DSL is finally active. That changes everything. If I had to pay every minute like in the older ISDN situation, I would maybe not do such experiments so relaxed. But with this package I can prepare the whole router now, use it now, put the DSL hardware already in place, and then just wait until someday the blinking LED becomes stable.

This is maybe a bit absurd, but also very german somehow: contract ready, hardware ready, paperwork ready, technology almost ready, and then the actual line activation takes forever.

Why I want a real router box

I do not want one Windows machine doing the internet and all other machines depending on that. I also do not want manual dial each time. I want a separate machine which is just there and does the gateway work. If it works good, nobody sees it. If it breaks, everybody sees it. This is exactly the kind of thing I like.

Also I want to learn Linux not only as desktop. Desktop is nice, but for me the interesting thing is always when one machine does a service for other machines. Then it gets serious. Then configuration is not decoration anymore.

The first setup is simple:

  • Cyrix Cx133 as the router
  • Teles 16.3 for ISDN
  • one NE2000 compatible network card for local LAN
  • SuSE 5.3
  • T-Online account
  • DSL hardware already connected, but DSL itself still sleeping somewhere in Telekom land

The LAN side is eth0. The ISDN side I will configure through the i4l tools once the login part is really clean.

Installing SuSE 5.3

SuSE installation feels big for a student machine because there are so many packages and YaST wants to help everywhere. But I must say, for this use case it is really practical. I do not want to compile every tiny thing right now. I want the machine up and then I want to start reading config files.

The nice thing is that SuSE 5.3 already has what I need for this direction:

  • kernel 2.0.35
  • VFAT support, finally good enough for me to jump in
  • isdn4linux pieces
  • YaST for basic setup
  • normal network tools and PPP stuff

The first days are not so elegant. I reinstall once because I partition stupidly. Then I configure the network wrong and wonder why nothing routes. Then I realize that reading the docs before midnight is much more productive than changing random options after midnight.

Still, the feeling is strong: this is possible. The machine is not powerful. The card is not luxury. But Linux is not laughing about the hardware. It takes the hardware seriously and tries to use it.

The Teles card and the small pain around it

The Teles 16.3 works, but not like a nice toy. It works like something you need to deserve first.

PnP is not really my friend here. Auto-detection is sometimes correct and sometimes not. I get into the usual dance with IRQ and I/O settings, and because the NE2000 clone is also not exactly a model citizen, I must be careful there are no collisions. When it finally stabilizes, I write down the values because I know I will forget them if I do not.

The card sits on S0 bus with a passive NT. That setup is physically very small. Short cable is important. At first I use a longer cable because it is just the cable I have on the desk. Then I get strange effects. D-channel sync comes, then some weird instability. I shorten the cable and suddenly the whole thing becomes much less dramatic. From this I learn again the old rule: with communication stuff, physical layer problems are always more stupid than the software problems.

When the ISDN side starts to work the feeling is really good. No modem noise. No analog nonsense. Digital and clean. I know 64 kbit/s is not much in the abstract, but compared to normal modem life it feels fast enough that one can do real things.

The strange situation with the DSL modem

The modem is already on the desk and it is maybe the best symbol for this whole phase. I already have the new thing. I can touch it. I can cable it. I can power it. But it is not mine yet in the practical sense, because the line in the exchange is not enabled.

So what happens is: I install the splitter, I connect the modem, I look at the LED, and it blinks. Every day it blinks. It is almost funny. It is like the house has a small promise lamp.

Because we already have the package, I can connect with ISDN under the same general tariff model and prepare everything. This is really useful. It means the whole router is not a waiting project. It is a live project from day one. The DSL modem is there as a future device, but the machine is already useful now through ISDN.

This also changes my mood when building it. I am not making a theoretical future router. I am making a real working box. If Telekom ever finishes the outside part, then maybe the uplink can change without rebuilding the whole idea from zero.

What I have running now

At this moment I keep it simple. I am still mostly happy that Linux is on the box and the basic line can come up. The stack is not fancy yet. It is more like this:

  • SuSE 5.3
  • isdn4linux
  • T-Online login
  • local Ethernet
  • a lot of notes on paper

I already know I want these things later:

  • dial on demand
  • IP masquerading for the LAN
  • maybe DNS cache
  • maybe Squid if memory allows it
  • and if DSL finally comes, then PPPoE and the same box continues

I do not know yet which part will be the most annoying. Right now I guess the Teles card. Maybe later I will say PPP is worse. Maybe both.

For now I am just happy that Linux finally starts for me with a version where VFAT is not a blocker anymore, the cheap ISDN hardware is usable, and the blinking DSL modem already stands on the desk like a small challenge.

Maybe next I write more when the dial-on-demand part is not so ugly anymore.

1998-10-03