[ILUG] Naive ADSL/WiFi questions (long (sorry!))?

[John Madden]

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On (21/06/07 13:02), Brian Foster said:
>  1. What is an “eligible line” (mine apparently is)?
>    The implication seems to be that all I have to do
>    is hook up the (supplied) modem to the existing
>    POTS line, and it “just works”.
> 
Something to do with line quality so you can get a decent amount of
signal at your end to support ADSL. I'm sure some other engineer type
could elaborate on this, but as a consumer, all you need to know is that
the supplier is happy that they can provide you ADSL over the phone line
you have.

>  2. The supplied modem is a (currently unknown) WiFi
>    unit.  I will be asking for details of this unit
>    (and its Linux compatibility); what should I be
>    looking for, and/or asking?
> 
Make sure (as already noted) that it has a wired ethernet connection,
and pick up a cheapo 100mb pci ethernet card for the desktop if it
doesn't already have one. You'll need it to set up the WiFi, and is
useful to confirm the router / ADSL are working before you go toying
with WiFi.

>     (I note that, according to the (downloaded) contract,
>    Linux is not (listed as) supported.  That does not
>    worry me (should it?), except if they insist Windross
>    must be used for diagnostics / upgrade / installation
>    or whatever, which is a non-starter:  I *** REFUSE ***
>    to run M$ shiteware.  100% ABSOLUTE REFUSAL!)
> 
As long as the router has an ethernet port, you should be fine. If it's
USB only, look elsewhere and avoid the hassle. Oh, and I'd agree with
you - if they absolutely require Windows, then politely explain that
you'll be going to a competitor because of this.

>  3. I presume I need some sort of a WiFi transceiver
>    connected to the Linux box.  At this point, I am
>    completely lost; I've no idea even exactly what
>    it is I need, other than _something_ since my box
>    has no networking connections of any kind at the
>    present time.  (Yes, it's that old!)
>     And how would I test the whatever(s?), _prior_ to
>    receiving the WiFi modem?  I.e., how could I confirm
>    that the Linux peer seems to be Ok?
> 
As was already stated, Atheros and Intel PRO wireless stuff seems to
work pretty well under Linux. Broadcom chipsets can be hit or miss.
Basically, as is usual with buying hardware for a Linux box, check if
it's supported before paying (uncle Google usually helps here).

I have some class of a USB WiFi adaptor thingy (at home, so don't have
make / model / chipset details to hand) which works with a one-line
patch to a driver (driver exists and supports the chipset, but just
needed the device ID to know it supported it). If you want details off
list, let me know.

As for checking if it works - dmesg, ifup <if>, then make sure you have
iwconfig and iwlist installed (wireless-tools I think is the package on
Debian), and use iwconfig <if> and iwlist <if> scanning. You'll also
need wpa-supplicant for WPA encryption, but get it working without the
encryption first!

>  5. One of many obvious Big Differences between dial-up
>    and ADSL/broadband is the “always on” nature of the
>    later.  That clearly means my box will be much more
>    likely to be attacked and/or compromised.  Currently,
>    I am using SUSE's Personal Firewall package(s?), and
>    also do not (intentionally) open up any services to
>    the outside world.
> 
A lot of the ADSL modems do NAT internally, so direct connections in
usually get stopped at that point. You should be safe enough with the
above, presuming you're not one to randomly download and run code others
say is cool :)

One thing to make sure of is that any methods of configuration for the
modem (generally http and / or telnet) are only open to the inside
network and not the internet at large. This is generally the default
case anyway.

>  6. And (w.r.t. Q5), how to I confirm/test that whatever
>    I do does what it should do, is useful/necessary, and
>    is not itself an (inadvertent?) problem?
> 
External machine and nmap your external address (usually given on some
web page served by the modem).

>  7. And (w.r.t. Q5 and Q6), besides keeping an eye on
>    the logs and for “strange behaviour”, what should I
>    do try and detect attacks / compromises, especially
>    those which have “succeeded” (in part or in full)?
> 
Unfortunately, most of the modems aren't open enough to allow you run
things like Snort on them to keep an eye on network traffic. Some have
their own in-built attack detection mechanisms, but in general, what
you've said above should cover you.

> 10. What am I not asking that perhaps I should be?
> 
Someone else mentioned PPPoE. I don't think you need to worry about
this, as the ADSL is usually terminated at the modem, and it's a
standard ethernet / wireless network internally. If the modem is a
bridge, then you need to terminate the ADSL at the Linux box, and need
PPPoE support there.

- -- 
John Madden -- john at jmadden.eu
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