Re: [aclug-L] PC-Card Linux Problems

[John Goerzen <jgoerzen@xxxxxxxxxxxx>]

Hmm, that is a dilly of a pickle.

It is suggestive that the same problem occurs under Windows.

OK, so the basic situation is:

* You have a laptop hooked up to an Ethernet without Internet
connectivity.  Your Ethernet has its own internal-only name service
and is the default route for your computer.

* You occasionally want to dial out to the Internet using a PCMCIA
modem card.

* The modem card works, but only if the Ethernet card is not present
as well.

Please correct me if my assumptions are incorrect.

Assuming I understand the situation correctly:

Jeremy Johnstone <jsjohnst@xxxxxxxxxxx> writes:

> their lack of any understanding or knowledge of Unix/Linux. (Secret is
> you have to figure out that they use CHAP authentication although their

Valuable tip!

> problems with my desktop machines. The problem I am running into is,
> with the new 100Base-T PC Card I use on my laptop. I own a Linksys
> 10/100 PCCARD and the card itself runs fine, but when I try to use PPP
> it locks up, doesn't load chat, and won't return to the prompt without
> me using control-c. I am currently using RedHat 5.0. I have checked and

This locks up the entire system, or just that particular console?

If possible, you may want to check /var/log/ppp.log or
/var/log/messages to see if anything "interesting" appears there.

> there is no IRQ conflict with the modem, and Minicom works fine.

In this case, I would suspect that there may be an IRQ conflict
between the some device and the PCMCIA controller, or (more likely)
that there is some sort of networking confusion going on when you
bring up PPP.

There are several issues at play:

1. Routing

When your system needs to communicate with others, it must know which
interface (Ethernet or PPP) to use to get it there.  On Ethernet, you
generally tell it to "put a packet on the wire" if it is going to a
machine on the same local physical Ethernet, or you tell it to send
the packet through a router if it is going somewhere else.  Generally, 
you set a default route such that everything that is not local goes to 
a router that knows where to send it.

The trick is that you generally set a default route for PPP as well,
since everything that is not local comes from some Internet site that
should be sent through your ISP.

If you have two interfaces with a default route set, problems can
arise.

2. IP addresses

If your internal Ethernet happens to use IP addresses that are also in 
use outside, bad things can happen to confuse your machine.

3. Name service

The name service is the way for your computer to lookup the numeric
identification (or IP address) of the machine it's trying to talk to.
Usually, your name service is provided by an ISP's server for PPP
connections.  If you have an internal-only Ethernet with no Internet
connection, you'd probably have internal-only nameservice.  But --
this name service may interfere with other requests if not done
properly.

Fortunately, these issues can be resolved in Linux.  I am not so sure
if Windows is powerful enough to properly deal with them.

We can get into resolution later.  I don't want to do any more typing
if my assumptions above turn out to be wrong :-)

-- 
John Goerzen   Linux, Unix consulting & programming   jgoerzen@xxxxxxxxxxxx |
Developer, Debian GNU/Linux (Free powerful OS upgrade)       www.debian.org |
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