The IP Pool you mentioned refers to the virtual IP address to be assigned to the device connected to the VPN, you can try to set it to 172.168.10.1/24, save it and then export the VPN file again, then import the VPN file on the PC side to connect to the VPN. You can refer to this link for configuration： https://www.tp-link.com/en/support/faq/3633/

  @Md-Ripon3 

First, thanks for the answer. But after I did everything in the link you send and tried their as well as your and other IP addresses for the IP pool, I still get the same error. 

  @Tedd404 

If you mean my VPN policy:

Name BMC

Status: Enable

Purpouse: Client to site VPN

VPN Type: VPN-Server OpenVPN

Accout Password: Enabled (also tried with disable)

Tunle mode: Split

Protocol: UDP

Service Port: 1194 (also tried 1196/ 1199)

Local Network Type: Network

Local Neworks: All

WAN: WAN/LAN4 (the Port, where my Internet goes in)

IP Pool: 192.168.0.150/24 (also tried many other IPs and check in clients if they are not already take)

Primary DNS: 8.8.8.8

Secondary DNS: 8.8.4.4

 

I of course also configured VPN user, when I activated Password in VPN policy section.

 

My WAN IP is: 188.10x.xxx.x

1. It is recommended to post a screenshot of the OpenVPN configuration and LAN status. 2. Maybe you can try to use other software to connect to OpenVPN, there are many such software on the internet.

  @Md-Ripon3 

In my FritzBox it shows under IPv4 DS-Lite-Tunnel and AFTR-Gateway: 2a02:xxx::xx:xxxx

and under IPv6 Adress: 2a02:xxx:xxxx:2::xxxx/64

                  IPv6 Präfix: 2a02:xxx:xxxx:xxxx::/59

 

Does it have to do anything with this?

  Oh and here also a picture of my Config. I physically as well as in the config, changed the incoming internet port to SFP+ Wan1.

I also tried other programs like Pritunl now, with the same result. I don't know what to do anyomore. If I am in the same network it manages to establish a connection. But as soon as I leave the network (what is part of the purpose of a VPN) I get no connection. I don't now what to do anymore?!

 

Your configuration doesn't seem to have any problems. tsl key negotiation fails probably due to the following reasons: 1. If there is still a gateway on the front end of the ER8411, it could be due to the NAT gateway not being configured with a port forwarding rule corresponding to the internal address of the OpenVPN server. Or the server address in the OpenVPN configuration file does not point to the public IP address of the gateway, but to the IP address of the ER8411. 2.PC's firewall is blocking access to openvpn, you may need to set up a whitelist or temporarily disable the firewall for OpenVPN to work properly.

  @Md-Ripon3 

After completely deactivating the PC firewall, it still does not work. I also think, it's like u said. It might very well be because the IP of the config file is not pointing to the TP-link router. But how do I change this?

In the Gateway in front of the TP-link Router, I already aktivated, that ports are automatically opening for that device.

  @Chris-Cross 

You can try to open the OpenVPN file in txt format, find the corresponding IP content and change it to the public IP of the router's front-end gateway.