Originally posted on NCOL.net

Create NAT Rule

• Click Configuration (top)
• Click Firewall (bottom-left)
• Click NAT Rules (middle-left)
• Select Add->Static NAT Rule
• Original

• Interface: inside
• Source: 10.80.5.47
• Translated
  • Interface: Outside
  • Select Use Interface IP Address
• Port Address Translation (PAT)
  • Check Enable Port Address Translation (PAT)
  • Protocol: TCP
  • Original Port: 3389
  • Translated Port: 3389
• Click OK

Create Access Rule

• Click Access Rules
• Select Add->Add Access Rule

• Interface: outside
• Action: Permit
• Source: any
• Destination: 10.80.5.47 or the object you created
• Service: tcp/3389
• Enable Logging: unchecked