vpn it's work but Some sites cannot be accessed but every time I connect to my VPN, I should run "sudo ifconfig ppp0 mtu 1500" How could I make it permanent?
You need to edit the interfaces file present under "/etc/network/"
Add the MTU size like below
Run the following command
I got this information from https://www.cyberciti.biz/faq/centos-rhel-redhat-fedora-debian-linux-mtu-size/