The kernel supports a number of hardware drivers for various
types of equipment. This section gives a short overview of the driver
families available, and the interface names used for them.
There are a number of standard names for interfaces in , which
are listed below. Most drivers support more than one interface, in
which case the interfaces are numbered, as in eth0,
The local loopback interface. It is used for testing pur-
poses, as well as a couple of network applications. It works
like a closed circuit in that any datagram written to it will
be immediately returned to the host's networking layer.
There's always one loopback device present in the kernel, and
there's little sense in having fewer or more.
The n-th Ethernet card. This is the generic interface name
for most Ethernet boards.
These interfaces access a D-Link DE-600 pocket adapter,
another Ethernet device. It is a little special in that the
DE-600 is driven through a parallel port.
The n-th SLIP interface. SLIP interfaces are associated with
serial lines in the order in which they are allocated for
SLIP; i.e., the first serial line being configured for SLIP
becomes sl0, etc. The kernel supports up to four SLIP inter-
The n-th PPP interface. Just like SLIP interfaces, a PPP
interface is associated with a serial line once it is con-
verted to PPP mode. At the moment, up to four interfaces are
The n-th PLIP interface. PLIP transports IP datagrams over parallel lines. Up to three PLIP interfaces are supported. They are allocated by the PLIP driver at system boot time and are mapped onto parallel ports.
For other interface drivers that may be added in the future, like ISDN,
or AX.25, other names will be introduced. Drivers for IPX (Novell's
networking protocol), and AX.25 (used by ham radio amateurs) are under
development, but are at alpha stage still.
During the following sections, we will discuss the details of using
the drivers described above.