PPTP server

sudo apt-get install pptpd

/etc/pptpd.conf

localip 192.168.3.1
remoteip 192.168.3.200-245

/etc/ppp/pptpd-options

ms-dns 8.8.8.8
ms-dns 8.8.4.4

/etc/ppp/chap-secrets

# client, server, secret, IP addresses
username pptpd "password" *

"client, server, secret, IP addresses" の順番で入力
server の名前は ="/etc/ppp/pptpd-options" のname

/etc/rc.local

sudo iptables -t nat -A POSTROUTING -s 192.168.3.0/24 -j MASQUERADE
exit 0

/etc/sysctl.conf

net.ipv4.ip_forward=1

sudo sysctl -p