Re: plip with mulinux

From: Sven Conrad (
Date: Sat Sep 02 2000 - 18:19:32 CEST

Hi Michele

Michele Andreoli wrote:
> On Tue, Aug 29, 2000 at 06:19:57PM +0200, Dumas Patrice nicely wrote:
> >
> > Well, if you define a network associated to an interface, you do static routing,
> > no ? Rustic static routing, it's true, but if the muBox is a router between
> > different subnets, each ones associated with a different interface, this could
> > be sufficient. I am not an expert at all in this stuff, so maybe I am wrong, but
> > it seems to me that routing a packet can be easily do with associating a natwork
> > and netmask to an interface ?
> On the list we have a network guru, but I do not remember the name (please,
> help us!).
I allways get a red hat, when saying things like this, but may be you
me in mind. I answered many Network questions, have done lots with
and manny people name me an expert (guru would be the first time)
Sorry for my late answering, but I started a new job in a new country
and so
have not the time to look into the list every day.

Sofar, I see two levels for this diskussion:

1. how to do this in the typical mulinux scripts, but therefor we have
   But thats not me!

2. What can be done with muliple interfaces.

I like the latter diskussion first, because it has a deep impact to the
I thing, it is easyer to write the scripts, if it is clear what they
sould do.

I can't see mulinux computers as major gateways in Company or
So what I see is, mulinix as Internet Gateway/Firewall at home, as
Playground for workgroops or things like this.

To bring a interface to work is very very easy. Do a ifconfig and add a
route. That's all. The eth, ppp and plip interface have liddle
for config commands but for route, a interface is a interface is a
So far ok. But that is mostly not sufficient, because you have only the
chance to alter the mulinux box. But if you want more than point to
connects, then EVERY box in the network needs all gateway routes! If
is, what you want, go ahead and set gateway routes for every subnet you
have and you are all set. (this depends totaly on the structure of the
entire network. E.g. gateways can be in a daisy chain!)
An other way is NAT. If the gateway use NAT, than you need no gateway
routes, only the NAT server needs to be known inside each Network it is
coupled to. I'am sure, I wrote muliple times before, this is what I
usualy do.

> What will happens if I
> 1. rename setup/network as setup/eth (eth cards and PCMCIA),
> 2. rename setup/ppp as setup/isp (internet connections)
> 3. write setup/plip and setup/ppp to handle only pc-to-pc serial/parallel
> connections by pointtopoint cable.
> 4. rewrite setup/network to handle only "route" commands?
Whow, great. Only one liddle point. You want "eth" for all bus-like
setups, what is ethernet with 100% coverage on mulinux. But linux can
more. But the idea to go for the properties of devices instead of the
incarnation is very good.
> Oh, you are thinking as I did: to put in only what is *global*
> or *common* to all network interfaces: nameserver, hostname, dhcp,
> routing and default gateway. Perfect.

One point: you can have as much gateways as you want. Default is only
the route,
where you are liked to the world. If you are not, then you can have
but none default. Please handle gateways more general. Problem, we have
to take
care for newbys.

> What is obscoure for me is that: suppose we have plip0, ppp0, ppp1, eth0, eth1
> up. What I can put in
> This script can extract info about interfaces dinamycally, i.e. using
> "ifconfig". Then, it can use the "route" command to enstablish and control
> the flux of packets between interfaces.
Here we are at a dificult question. Every interface needs at least one
but can have more!
[eth0 =]
route add -net netmask
route add -net netmask gw
route add -net netmask gw

which means, this box is a gateway to a "backbone" with two other
and there subnets behind! All these routes go to eth0!!! (route sees
allone, because the gw's are in the 1 net)

BTW: could a cat /proc/net/dev be easyer to parse than the output of

Last point. By now, I can not make much testing. I guess, late in
Oktober, all
my computers are up again. Then I can make manny, allso complex tests
with up
to 7 computers. Ideas are wellcome.

Ok, I will study all the other mail a liddle more.


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