Questions : CCNA Exam Preprations

You have an internal web server that must be accessed from the corporate Internet connection. This internal web server has the IP address 172.16.55.10. The router accesses the Internet through the FastEthernet0/1 interface. What NAT syntax is necessary to forward HTTP requests to the internal web server?

A. ip nat outside destination tcp 80 fastEthernet0/1 172.16.55.10 80

B. ip nat inside source static tcp 172.16.55.10 80 interface fastEthernet 0/1 80

C. ip nat outside source tcp 80 172.16.55.10 80 interface fastEthernet0/1 80

D. ip nat inside destination static tcp 172.16.55.10 80 interface fastEthernet 0/1 80


B. The ip nat syntax can be quite cryptic because the Cisco router gives you plenty of flexibility with the form and directions of NAT translation. In this case, we are looking to create a Static NAT translation to allow TCP port 80 (HTTP) to pass through the Cisco router to the internal web server. There are two ways to accomplish this; we can create a Static NAT translation from the inside perspective or from the outside perspective. In this question, the only correct answer is the translation performed from the inside: ip nat inside source static tcp 172.16.55.10 80 interface fastEthernet 0/1 80. If we were to perform the Static NAT translation from the outside perspective, we would not be given the option to choose to translate from an interface (fastEthernet 0/1, in this case). Answers A, C, and D would result in an invalid syntax message.