Asus RT-AC87U no ping with NAT Enabled

[run4you]

Hi. I have a router Asus RT-AC87U with Merlin firmware 380.66_6 and I have a problem. When i activate NAT from Basic Config i don't have ping in wan router ip. If i disable nat the ping to wan is working without problem. The firewall from router is turned off. I use static IP. I test another router RT-AC5300 with Merlin firmware and the issue not appear. What is the problem? Thank you.

 

[run4you]

Hi. I change from router firewall nat loopback from Merlin to Asus and ping is working but now the vpn pptp is not working. I try to connect with pptp client and connection is not working. If i disable again nat from basic config is working. With nat disable all router clients don't have internet connection. Thank you.