How to fix the problem of not working internet when connecting to VPN PPTP?

Question

VPN

Configured on centos 7 server pptpd
added to iptables

-A INPUT -i eth0 -p tcp --dport 1723 -j ACCEPT
-A INPUT -i eth0 -p gre -j ACCEPT

When connected to pptp, it connects and there is a connection, but the Internet stops working, apparently the traffic is not wrapped in the pptp network,
how to fix it?

Answer 1

In the server settings, you need to enable packet routing.
nano /etc/sysctl.conf
allow exchange between network interfaces, add
net.ipv4.ip_forward = 1
Taken from here
www.unitec.com.ua/nastrojka-pptp-vpn-na-centos-7
Firewall -
firewall-cmd --permanent --add-masquerade
firewall-cmd --zone=public --add-port=1723/tcp --permanent
firewall-cmd --permanent --direct --add-rule ipv4 filter INPUT 0 -p gre -j ACCEPT
firewall -cmd --permanent --direct --add-rule ipv6 filter INPUT 0 -p gre -j ACCEPT
firewall-cmd --reload
Taken from here
https://sysadminblog.ru/linux/2018/07/11/prostoy-p ...

Answer 2

route add default gw metrics etc.