Kernel Configuration - Part XIX

We’ve had a couple of days in which the kernel configuration tips applied only
to a small group of users. Today, we’ll look into an area that will apply to
most - the Network device support section.

According to the kernel configuration help sections, you’ll need to include
network device support if you intend to connect your computer to the Internet
via a network card, SLIP, PPP, PLIP, or AX.25/KISS (amateur radio links). In
other words, if you’re going to connect via a cable modem or a dialup modem,
you’ll need to include network device support in your kernel. As always, this
can be by building the code into the kernel or by creating a loadable module.

There are many options in the network device section. As is the norm, these are
specific to the device types and protocols you’ll be using to connect your
computer to a network. The first is ARCNet. ARCnet isn’t really ethernet and, as

with the others, requires specific hardware. Dummy net driver support is, in
essence, the network equivalent to /dev/null. It’s a ‘bit bucket’ in which
packets sent to this device get completely ignored. Bonding device support
allows you to couple two ethernet devices together, acting as a single double
speed device. For bonding device support to work, it must be supported at the
connection - the machine to which you’re connecting. EQL support provides a
similar feature for serial lines such as telephone lines. Again, in order to use

two modems as a single device (and, theoretically, double your speed) your ISP
must support the protocol. TUN/TAP and Ethertap are both relatively rare. You’re

not likely to need support for either. General Instruments Surfboard 1000
support is a bit more common, providing support for a specific internal cable
modem. By this high level list of devices alone, you can again see the value of
knowing the hardware in your machine.

The next major section of the network device kernel configuration deals with
ethernet cards. If you’re connecting to the Internet via a cable modem or DSL,
you’ll need an ethernet card. You’ll also want ethernet capabilities if you’re
connecting your machine to an local network. For the past several years, I’ve
used 3Com 3C90x cards almost exclusively. They’re relatively cheap, very
reliable and supported by default in most Linux distributions. In any event, the

10/100 Mb ethernet section of the network device configuration is where you’ll
choose the specific driver for your ethernet card. That’s also the case with the

1000 Mb section.

If you’re on a dialup to an ISP using the Point to Point Protocol (PPP), you’ll
need to include PPP support. In effect, this creates the basic kernel interface
to your modem. By itself, this kernel element won’t connect you to your ISP, but

it’s a piece that’s necessary as part of the dialup configuration in total.
Within this section, you’ll find several “fine-tuning” options. Again, these are

specific to devices and protocols - elements you’ll need to know in order to
utilize them fully.

Very few ISP still use the SLIP protocol. If, however, your ISP hasn’t made the
change to the much more efficient PPP protocol, you’ll need to include SLIP in
your kernel configuration. It’s a good idea to check with your ISP for
details.

The network device configuration section also contains options for wireless LAN
support, token ring, WAN interfaces, and PCMCIA devices. Among these, the most
commonly used in home machines is PCMCIA network support. PCMCIA cards are the
small hardware devices used primarily in laptops. If your Linux computer is a
laptop, you’ll want to include PCMCIA support in the kernel configuration.

In the earlier kernel configuration series, I noted that it’s tough to give you
a set of standard configuration options. I took some heat for that. The network
device section makes the case clearly. With the broad array of available
hardware and protocols, it’s impossible to definitively recommend one
configuration over another. It all depends on your hardware and the type of
network support you’ll be using. In the end, the best “static” recommendation I
can make is this: if you’re unsure about device or protocol selection, a) find
out as much about your hardware as possible or b) use the defaults in the
network device section. The chances of success are far better with the
former.

Monday, we’re on to Amateur Radio support.