simple isdn4linux PPP FAQ .. to be continued .. not 'debugged' Q: pppd,ipppd, syncPPP , asyncPPP .. what is that ? what should I use? A: The pppd is for asynchronous PPP .. asynchronous means here, the framing is character based. (e.g when using ttyI* or tty* devices) The ipppd handles PPP packets coming in HDLC frames (bit based protocol) ... The PPP driver in isdn4linux pushes all IP packets direct to the network layer and all PPP protocol frames to the /dev/ippp* device. So, the ipppd is a simple external network protocol handler. If you login into a remote machine using the /dev/ttyI* devices and then enable PPP on the remote terminal server -> use the 'old' pppd If your remote side immediately starts to send frames ... you probably connect to a syncPPP machine .. use the network device part of isdn4linux with the 'syncppp' encapsulation and make sure, that the ipppd is running and connected to at least one /dev/ippp*. Check the isdn4linux manual on how to configure a network device. Q: when I start the ipppd .. I only get the error message "this systems lacks PPP support" A: check that at least the device 'ippp0' exists. (you can check this e.g with the program 'ifconfig') The ipppd NEEDS this device under THIS name .. If this device doesn't exists, use: isdnctrl addif ippp0 isdnctrl encap ippp0 syncppp ... (see isdn4linux doc for more) ... A: Maybe you have compiled the ipppd with another kernel source tree than the kernel you currently run ... Q: when I list the netdevices with ifconfig I see, that my ISDN interface has a HWaddr and IRQ=0 and Base address = 0 A: The device is a fake ethernet device .. ignore IRQ and baseaddr You need the HWaddr only for ethernet encapsulation.