• http://ru.wikipedia.org/wiki/PPPoE
• Сервисы Gateway и routing
• Сервис NAT
• Сервис Firewall Конфигурация для шлюза WAN - LAN
• Сервис PPP

root@gate:~# apt install pppoe

root@gate:~# modprobe pppoe

root@gate:~# cat /etc/modules

...
pppoe

root@gate:~# cat /etc/ppp/pppoe-server-options

+chap
# ms-dns 192.168.X.10

root@gate:~# pppoe-server -I eth0

или

root@gate:~# pppoe-server -I eth0 -R 192.168.100+X.1

можно прописать в /etc/rc.local

root@gate:~# tail -f /var/log/syslog

[gate:~] # cat /etc/rc.conf

...
pppoed_enable="YES"
pppoed_flags="-P /var/run/pppoed.pid -l inet"
pppoed_interface="em0"

[gate:~] # /etc/rc.d/pppoed start

[gate:~] # tail -f /var/log/ppp.log

Скрипт не работает (проверено до 7.3 включительно)

[gate:~] # killall pppoed

• Ubuntu 17.10.1 - как настроить DSL подключение к интернету?

[gate:~] # cat /etc/ppp/ppp.conf
isp:
 set ifaddr 10.0.0.1/0 10.0.0.2/0
 set device PPPoE:lnc1
 set authname studentX
 set authkey passwordX
 set dial
 set login
 add default HISADDR

[gate:~] # route delete default

[gate:~] # ppp -ddial isp

[gate:~] # killall ppp

[gate:~] # /etc/rc.d/routing restart

# apt install pppoe

# ip l set eth0 up

# sysctl net.ipv4.ip_forward=1

# pppoe-relay -S eth1 -C eth0