Linux PPP HOWTO Prev Chapter 12. Configuring your modem and serial port Next 12.2. Serial Port Names Historically, Linux used cuaX devices for dial-out and ttySx devices for dial-in. The kernel code that required this was changed in kernel version 2.0.x and you should now use ttySx for both dial in and dial out. I understand that the cuaX device names may well disappear in future kernel versions. Prev Home Next Configuring your modem and serial port Up Configuring your modem