Linux VPS vpn setup error 800 solution

After the vpn is installed, a 800 error is prompted when you connect to the vpn using windows. Generally, the firewall does not open the corresponding Port. In this case, add the port to the firewall. The code is as follows:

Iptables-a input-m state-state NEW-m tcp-p tcp-dport 1723-j ACCEPT
Service iptables save (save)
Service iptables restart (restart the service to make the configuration take effect)

Tip: If you are using a linode vps, the following error may occur when you restart the service: Setting chains to policy ACCEPT: security raw nat [FAILED] filter
This is because Linode adds a security rule chain to iptables, but Centos does not. The solution is as follows:
Use code vi/etc/init. d/iptables to edit/etc/init. d/iptables and find

For I in $ tables; do
Echo-n "$ I"
Case "$ I" in
Raw)
$ IPTABLES-t raw-p prerouting $ policy \
& $ IPTABLES-t raw-p output $ policy \
| Let ret + = 1
;;

Add the following content to "case" $ I "in:

Security)
$ IPTABLES-t filter-p input $ policy \
& $ IPTABLES-t filter-p output $ policy \
& $ IPTABLES-t filter-p forward $ policy \
| Let ret + = 1
;;

The final result is as follows:

For I in $ tables; do
Echo-n "$ I"
Case "$ I" in
Security)
$ IPTABLES-t filter-p input $ policy \
& $ IPTABLES-t filter-p output $ policy \
& $ IPTABLES-t filter-p forward $ policy \
| Let ret + = 1
;;
Raw)
$ IPTABLES-t raw-p prerouting $ policy \
& $ IPTABLES-t raw-p output $ policy \
| Let ret + = 1
;;