11.4 Configuring and Troubleshooting PAT on the Cisco 700 Router
11.4.2 PAT porthandler operation

If users need to access a specific remote server on the private network, PAT allows packets with a specific well-known port number to get through (for example, FTP or Telnet), as shown in the Figure. Only one server of each type (FTP, Telnet, and so on) can be on the remote LAN. Use a static address for the remote servers so they can be found. You can set a static host route at the central site to get to the remote server. On Cisco 700 series router running PAT, either a static or dynamic address can be used.