@dbSoft Hello, you can provide information about your ISP and the model number of your ISP router.

And you can ask your ISP to provide the model number of your ISP router, cause we don't know whether it's a modem or a router.

We can discuss the VPN later when you get the device type and model number from your ISP.

And for port forwarding, generally the connection is between the ISP device's WAN port and the ISP device's port which is connected to your ER605. So the data will be transmitted from the WAN port to your ER605. And if you set VPN on ER605, the date will be transmitted again from its WAN port to LAN.

  @Dahliana 

Thank you very much for yoyr reply.

I attach device information.

  @dbSoft Seems that your device is  ZTE ZXHN F670L, and your router get an IP address as 192.168.1.x.

And I have checked the specifications of it. This router supports the VPN function, so maybe there's no need for you to set VPN on ER605.

Here's the specifications: http://ztegpon.cz/pdf/ZXHN%20F670L%20datasheet.pdf

So you can consult your ISP or ZTE on how to set VPN to meet your needs.

  @Dahliana 

Thanks again for reply.

I know , actually this is our store modem.

We needbto see if vpn works so proposed to customers.