When internal users access the external network, NAT server translates only internal IP addresses to external IP addresses, whereas NAT static translates both internal IP addresses and ports to external IP addresses and ports.
The enterprise requires that its internal users can access the external server and external users can access its internal server, as shown in Figure 1. If you configure both NAT server and Easy IP on the router, it translates only internal IP addresses to external IP addresses when internal users access the external network. This may result in a failure to set up stream tables. In this case, you are advised to configure NAT static but not NAT server on the router.
Figure 1 Networking diagram of NAT server and Easy IP