What can Destination NAT (dstnat) be used to achieve?

Destination NAT (dstnat) is primarily used to direct incoming traffic from the Internet to a specific server within a local network. This capability allows for the proper routing of requests, such as when a client attempts to access a web server hosted internally. When you set up dstnat, you can specify that traffic arriving on a particular port or IP address should be redirected to a different IP address and possibly a different port within your local network. This is essential for services that need to be accessed from outside the firewall, enabling external users to reach internal resources without exposing the entire local network.

The other options provided do not accurately describe the primary function of Destination NAT. While changing the destination port is a function of routing traffic, it is more accurate to say that DSTNAT facilitates access to internal servers rather than solely modifying ports or hiding network structures.