Wide Area Networks (WANs), such as X.25, frame relay and leased
lines, are used to interconnect Local Area Networks (LANs) over vast
distances with data transfer rates significantly higher than those
achievable with commonly used asynchronous modem connections.
Usually, a quite expensive external device called a `WAN router' is
needed to connect to a WAN.

As an alternative, WAN routing can be built into the Linux kernel.
With relatively inexpensive WAN interface cards available on the
market, a perfectly usable router can be built for less than half
the price of an external router. If you have one of those cards and
wish to use your Linux box as a WAN router, say Y here and also to
the WAN driver for your card, below. You will then need the
wan-tools package which is available from <ftp://ftp.sangoma.com/>.
Read Documentation/networking/wan-router.txt for more
information.

To compile WAN routing support as a module, choose M here: the
module will be called wanrouter.

If unsure, say N.

source code:

net/wanrouter/