USG 5500 version V300R001C00SPC700.
Customer reported that is trying to configure nat server and configuration it fail to take effect.
nat server 0 vpn-instance vp1 zone untrust global 126.96.36.199 inside 10.1.1.1 no-reverse vpn-instance vp2
Ping to internal server via 188.8.131.52 failed.
Nat server having inside address in one vpn-instance and outside ip address into another vpn-instance is not currently supported on USG firewall
We advice to use the working scenario when the server resides in the public VPN, and the client resides in another VPN instance, only one vpn-instance parameter is specified.
For example, nat server vpn-instance vpn1 zone untrust global 184.108.40.206 inside 220.127.116.11.
Or configure nat server for the situation when inside address and outside address reside in the same vpn-instance.