21.1 Synopsis

FreeBSD has a number of ways to link one computer to another. To establish a network or Internet connection through a dial-up modem, or to allow others to do so through you, requires the use of PPP or SLIP. This chapter describes setting up these modem-based communication services in detail.

After reading this chapter, you will know:

• How to set up user PPP.

• How to set up kernel PPP.

• How to set up PPPoE (PPP over Ethernet).

• How to set up PPPoA (PPP over ATM).

• How to configure and set up a SLIP client and server.

Before reading this chapter, you should:

• Be familiar with basic network terminology.

• Understand the basics and purpose of a dialup connection and PPP and/or SLIP.

You may be wondering what the main difference is between user PPP and kernel PPP. The answer is simple: user PPP processes the inbound and outbound data in userland rather than in the kernel. This is expensive in terms of copying the data between the kernel and userland, but allows a far more feature-rich PPP implementation. User PPP uses the tun device to communicate with the outside world whereas kernel PPP uses the ppp device.