In order to establish a PPP link between two computers using the telephone line as medium for data transmission, you will need to install and configure a modem device in each computer you plan to connect. On the other hand, if you're planning to use PPP to connect the same computer to different networks simultaneously (e.g., to build a proxy between them), you will need to install and configure one modem device for each different network you plan to establish such simultaneous connection in the same computer. To install a modem device in the computer, you need to attach the modem hardware to the computer and later the telephone line to the modem hardware. To attach the modem hardware to your computer, you need to connect the serial or USB cable that comes from the modem hardware to the appropriate input on your computer (whether serial or USB). To connect the modem hardware to the telephone line, you need to unplug the cable that connects your telephone device and plug it on the modem device, specifically in the port reserved for data transmission. Later, using a similar cable, you could connect your telephone device to the modem's telephone port, so you can realize telephone calls when no data transmition take place through modem's data port. To be on the safe side, do everything related to hardware installation with the computer turned off. Then, when everthing has been put in place, turn the computer on. Once the operating system is up and running, you can verify the modem hardware using either the lsusb or lspci commands, based on whether you attached the modem device to an USB or serial port, respectivly. These commands need to be run with administrative privileges, thus, you probably need to do sudo on them or login as root user in order to execute them. For example, assuming you logged in as root user and you installed an USB modem hardware as mentioned before, the output of lsusb command would be similar to that following: Bus 003 Device 001: ID 0000:0000 Bus 001 Device 001: ID 0000:0000 Bus 001 Device 002: ID 058f:6366 Alcor Micro Corp. Multi Flash Reader Bus 002 Device 001: ID 0000:0000 Bus 005 Device 003: ID 06e0:f104 Multi-Tech Systems, Inc. MT5634ZBA-USB MultimodemUSB (new firmware) Bus 005 Device 001: ID 0000:0000 Bus 005 Device 002: ID 046d:c018 Logitech, Inc. Optical Wheel Mouse Bus 004 Device 001: ID 0000:0000 The relevant line in this output is that one mentioning the existence of your modem. For example, Multi-Tech System, Inc. MT5634ZBA-USB MultimodemUSB (new firmware) I want to thank my friend Brians Suarez Alonso for bringing this modem hardware to me and for his paitient, resisting my repetitive calls at night to realize connection tests. . This line confirms that your modem hardware is supported by &TCD; and it is possible to transmit data through it. Otherwise, if the modem you installed doesn't appear in this list, it is probably because such hardware is not supported by &TCD;, yet. Once you have confirmed the modem hardware has been installed in the computer (either client or server), you need to determine the device name the operating system assigned to it. This information is required by programs like mgetty and wvdial, so they can know what device to talk to. Assuming you've connected your modem device through an USB port, the operating system will assign the the /dev/ttyACM0 device file to talk to it. On the other hand, assuming you've connected your modem device through a serial port, the operating system will use the /dev/ttyS0 device file to talk to it. To be absolutly sure about what device name the operating system assigned to your modem hardware, you can use the lshal command from hal package. Inside &TCD;, modem devices can be configured using the system-config-network tool. This tool is a manages modem configuration files under the /etc/sysconfig/network-scripts and /etc/wvdial.conf. Inside /etc/sysconfig/network-scripts, modem configuration files can take different file names. To identify them you need to open the file and checking the value set on DEVICE variable. This variable can take values like ppp0 for the first modem device, ppp1 for the second modem device, and so on for other modem devices. The configuration files of modem devices may vary based on whether the computer is acting as server, client or both. When you configure the modem device on the server computer, you should take care of specifying both the IP address (IPADDR) and the network mask (NETMASK) inside the configuration file. Otherwise, the established connection might end up having the wrong IP information you need to transfer data correctly through it, assuming the other end isn't configured to specify it. When you configure the modem device on the server computer, there is no need for you to set any configuration related to wvdial, unless you be thinking to make your server computer to act as a client of another server computer. In fact, in the server computer, you can create the modem configuration file by yourself based on the information provided at /usr/share/doc/initscripts-*/sysconfig.txt When you configure the modem device on the client computer, you don't need to take care of specifying either the IP address or network mask because the server computer will assign them for you. The assignment of client computer IP address is configured by ppp daemon when it is executed by mgetty after an incoming call has arrived to modem's port. Modem configuration file # Please read /usr/share/doc/initscripts-*/sysconfig.txt # for the documentation of these parameters. TYPE=modem DEVICE=ppp0 BOOTPROTO=none ONBOOT=no USERCTL=yes PEERDNS=yes AC=off BSDCOMP=off VJCCOMP=off CCP=off PC=off VJ=off LINESPEED=115200 MODEMPORT=/dev/ttyACM0 PROVIDER=ProviderName DEFROUTE=yes PERSIST=no PAPNAME=faith WVDIALSECT=ProviderName MODEMNAME=Modem0 DEMAND=no IPV6INIT=no IDLETIMEOUT=600 NETMASK=255.255.255.0 IPADDR=192.168.1.1