Configuring PPP Dial-in
For a more comprehensive PPP-HowTo see: tldp.org
Identifying the Modem port
External
Once logged in to the client machine, you should grep through/var/log/messages to search for a tty string. If you find something similar to this:
ttyS00 at 0x03f8 (irq = 4) is a 16550A |
This means there is one com port, and the mode will be attached to /dev/ttyS0
 | If there are more than one com ports, you will have to find out which com port the modem is attached to (com 0, 1, 2). This number will be similar to the device in /dev, id est: com 0 = /dev/ttyS0; com 1 = /dev/ttyS1 |
Internal
With an internal modem, you may find the correct modem port from output of lspci -vv.
02:09.0 Communication controller: Lucent Microelectronics Venus Modem (V90,56KFlex)
Subsystem: Action Tec Electronics Inc: Unknown device 0480
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B-
Status: Cap+ 66Mhz- UDF- FastB2B+ ParErr- DEVSEL=medium TAbort- TAbort- MAbort- SERR- PERR-
Latency: 0 (63000ns min, 3500ns max)
Interrupt: pin A routed to IRQ 21
Region 0: Memory at f9fffc00 (32-bit, non-prefetchable) [size=256]
Region 1: I/O ports at dc00 [size=256]
Region 2: I/O ports at d800 [size=256]
Region 3: I/O ports at d4f8 [size=8]
Capabilities: [f8] Power Management version 2
Flags: PMEClk- DSI+ D1- D2+ AuxCurrent=0mA PME(D0-,D1-,D2+,D3hot+,D3cold-)
Status: D0 PME-Enable- DSel=0 DScale=0 PME- |
You will notice the IRQ 21 line. You now need to iterate through /dev/ttyS* devices with setserial until you find a matching IRQ, as seen below:
# setserial /dev/ttyS4 /dev/ttyS4, UART: 16550A, Port: 0xdc00, IRQ: 21 |