quick'n dirty howto: connect to a serial-console device e.g. router/switch using the programm minicom, linux
1) have a look in the output of dmesg | grep tty [ ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A [ ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A [ ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A 2) start the program "minicom" 3) enter the menu ctrl-A-o 4) change the settings of the serical port
example:
| A - Serieller Anschluss : /dev/ttyS0 | | B - Pfad zur Lockdatei : /var/lock | | C - Programm zur Rufannahme : | | D - Programm zum Wählen : | | E - Bps/Par/Bits : 9600 8N1 | | F - Hardware Flow Control : Ja | | G - Software Flow Control : Nein 5) press ESC and enter settings for Modem and Dialup 6) change Modem Initialisation to : ~^M~ (simply remove the: A - Modem-Initialisierung ~^M~AT S7=45 S0=0 L1 V1 X4 &c1 E1 Q0^M ) 7) press ESC and save your settings as "dfl" 8) press CTRL-A-x to exit mincom, and start it again, it sould show status "online"