Настройка "обратного звонка" посредством USER PPP в Unix-подобных системах.

Пример файла конфигурации ppp (обычно это находится в /etc/ppp/ppp.conf):

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default:
set log Phase Chat LCP IPCP CCP tun command
ident user-ppp VERSION (built COMPILATIONDATE)

# Ensure that "device" references the correct serial port
# for your modem. (cuaa0 = COM1, cuaa1 = COM2)
#
set device /dev/cuaa0

set speed 115200
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \
\"\" AT OK-AT-OK ATE1Q0 OK \\dATDT\\T TIMEOUT 40 CONNECT"
set timeout 180 # 3 minute idle timer (the default)
enable dns # request DNS info (for resolv.conf)

dialout:
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \
\"\" AT OK-AT-OK ATE1Q0L1M1 OK \\dATDT\\T TIMEOUT 40 CONNECT"
set timeout 180
set callback cbcp e.164 USER_PHONE_NUMBER
set cbcp USER_PHONE_NUMBER
set phone ISP_PHONE_NUMBER
set authname USER_LOGIN
set authkey USER_PASSWORD

dialin:
set dial "ABORT BUSY ABORT NO\\sCARRIER TIMEOUT 5 \
\"\"TIMEOUT 30 RING ATA CONNECT"
set timeout 180
disable pap chap
set authname USER_LOGI
set authkey USER_PASSWORD
set callback none
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Ввести в командной строке последовательно:

/usr/sbin/ppp -background dialout
/usr/sbin/ppp -background dialin