Ho ricompilato il kernel attivando il supporto per il modulo Hisax ed in particolare ho usato i seguenti parametri:

CONFIG_ISDN     <M>
CONFIG_ISDN_DRV_HISAX     <M>
CONFIG_HISAX_16_3     <Y>
CONFIG_EURO     <Y>

Poi ho settato  <Yes>  a:

CONFIG_ISDN_PPP
CONFIG_ISDN_PPP_VJ
CONFIG_ISDN_PPP_MPP
CONFIG_ISDN_AUDIO

Ho installato i pacchetti (rpm):
 

• isdn4k-utils (ver 2.1.b1)
• isdn4net

Quest'ultimo fornisce un po' si script utili per il caricamento dei moduli "isdn4linux" (in /etc/rc.d/init). Esso carica i moduli in base al file di configurazione isdn (in /etc/sysconfig ...).
Nella file di configurazione isdn settare corretamente IRQ (normalmente 10) e
IO (normalmente 0x180) oltre ad altri parametri relativi alla linea ISDN in Italia.

Questi pacchetti sono disponibili nella directory contrib di RedHat o e possibile cercarli sul megadatabase Rufus della W3C: http://rufus.w3.org/linux/RPM/

Gli script per la connessioni li ho costruiti a partire dai file
rc.isdn.syncppp e rc.isdn.syncppp.1 forniti nel pacchetto isdn4k-utils (usr/doc/ ...)

Lo script che uso per la connessione e il seguente (sostituire opportunamente i propri numeri di telefono e indirizzi IP):
----------------------------------------------------------
#!/bin/sh
#
# BE SURE TO EDIT THIS FILE BEFORE USING IT !!!!!
# this is an example script to use with isdn4linux
# compiled into kernel
#
# don't forget to edit the files
#     /etc/ppp/pap-secrets or
#     /etc/ppp/chap-secrets
#

LOCAL_NUMBER="99999999"
REMOTE_NUMBER="13246789"
LOCAL_IP="0.0.0.0"
REMOTE_IP="194.243.154.62"
DEVICE="ippp0"

SYSPATH="/sbin"
TELESCTRL="$SYSPATH/telesctrl"
ISDNCTRL="$SYSPATH/isdnctrl"

$TELESCTRL Teles163 1 4      # enable verbose '4' mode
echo "****** Starting ISDN ... "
$ISDNCTRL addif  $DEVICE            # Create new interface 'DEVICE'
# $ISDNCTRL addphone $DEVICE in $REMOTE_NUMBER  # Set incoming phone-number
$ISDNCTRL addphone $DEVICE out $REMOTE_NUMBER   # Set outgoung phone-number
$ISDNCTRL eaz $DEVICE $LOCAL_NUMBER             # Set local EAZ ..
$ISDNCTRL l2_prot $DEVICE hdlc      # for sync PPP: set Level 2 to HDLC
$ISDNCTRL l3_prot $DEVICE trans     # not really necessary, 'trans' is default
$ISDNCTRL encap $DEVICE syncppp     # encap the IP Pakets in PPP frames
$ISDNCTRL huptimeout $DEVICE 600    # Hangup-Timeout is 600 sec.
$ISDNCTRL chargehup $DEVICE off     # Hangup before next Charge-Info
$ISDNCTRL secure $DEVICE on         # Accept only configured phone-number

$SYSPATH/ifconfig $DEVICE $LOCAL_IP pointopoint $REMOTE_IP metric 1
$SYSPATH/route add default dev $DEVICE

# start the (new) deamon:
# -----------------------
# 'user myusername' : set username to get the right password from the
#    pap/chap-secrets file(s)
# ipcp-accept-local ipcp-accept-remote : accept every IP address
# -vjccomp -ac -pc  : _my_ remote side doesn't support this, so disable it
# -bsdcomp : i4l-syncPPP driver doesn't support bsd-compression
# debug    :  enable debugging, WARNING: ipppd will also log your password
# useifip  : get IP address information form the network interface
# /dev/ippp0 /dev/ippp1 /dev/ippp2 : connect to 3 devices for max.
# 
# Se e' gia attivo il demone non lo rilancia

if [ ! -e /var/run/ipppd.pid ]; then
echo "****** Starting ipppd ..."
$SYSPATH/ipppd /dev/ippp0  &
fi
----------------------------------------------------------

Questo script usa il file ioptions in /etc/ppp e il file pap-secrets:

Il file ioptions:
----------------------------------------------------------
user myuser
ipcp-accept-local
ipcp-accept-remote
noipdefault
defaultroute
-vj
#-vjccomp
#-ac
#-pc
-detach
mtu 1500
mru 1500
#-bsdcomp
debug
----------------------------------------------------------

Per disconnettermi uso il seguente script:
----------------------------------------------------------
#!/bin/sh
#
# BE SURE TO EDIT THIS FILE BEFORE USING IT !!!!!
# this is an example script to use with isdn4linux
# compiled into kernel
#
# don't forget to edit the files
#     /etc/ppp/pap-secrets or
#     /etc/ppp/chap-secrets
#

LOCAL_NUMBER="99999999" #
REMOTE_NUMBER="123456789"
LOCAL_IP="0.0.0.0"
REMOTE_IP="194.243.154.62"
DEVICE="ippp0"

SYSPATH="/sbin"
TELESCTRL="$SYSPATH/telesctrl"
ISDNCTRL="$SYSPATH/isdnctrl"

VERSION=`cat /proc/version | awk '{ print $3 }' `

# when setting the environment variable MODPATH you
# can omit the full path.
echo "****** Stop ISDN ..."
$SYSPATH/ifconfig $DEVICE down
$ISDNCTRL delif  $DEVICE
----------------------------------------------------------

Installando i pacchetti isdn4linux si ha disponibile, sotto X, l'utility "isdnbutton" con il semaforo rosso quando al scheda non e startata, giallo se la scheda e attiva e verde se la connessione e attiva.