NAT Questions

Note: If you are not sure about NAT PAT, please read our Network Address Translation NAT Tutorial.

Question 1

Question 2

Explanation

Maybe this question wanted to ask “which IP address is the source IP at the receiving side?” as there are two correct answers for inside local IP address (10.4.4.4 & 10.4.4.5) so they cannot be the correct answer.

Question 3

Explanation

By adding the keyword “overload” at the end of a NAT statement, NAT becomes PAT (Port Address Translation). This is also a kind of dynamic NAT that maps multiple private IP addresses to a single public IP address (many-to-one) by using different ports. Static NAT and Dynamic NAT both require a one-to-one mapping from the inside local to the inside global address. By using PAT, you can have thousands of users connect to the Internet using only one real global IP address. PAT is the technology that helps us not run out of public IP address on the Internet. This is the most popular type of NAT.

An example of using “overload” keyword is shown below:

R1(config)# ip nat inside source list 1 interface ethernet1 overload

Question 4

Explanation

NAT use four types of addresses:

* Inside local address – The IP address assigned to a host on the inside network. The address is usually not an IP address assigned by the Internet Network Information Center (InterNIC) or service provider. This address is likely to be an RFC 1918 private address.
* Inside global address – A legitimate IP address assigned by the InterNIC or service provider that represents one or more inside local IP addresses to the outside world.
* Outside local address – The IP address of an outside host as it is known to the hosts on the inside network.
* Outside global address – The IP address assigned to a host on the outside network. The owner of the host assigns this address.

Question 5

Explanation

The “ip nat inside” command was wrongly configured with inside local address of 192.168.11.254 while it should be 192.168.11.11, which is the IP address of the web server.

Question 6

Explanation

The command “ip nat inside source list 1 pool mypool” (notice the keyword “inside”, not “outside”).

This command translates all source addresses that pass access list 1, which means a source address from 10.10.0.0/24, into an address from the pool named mypool (the pool contains addresses from 192.168.3.1 to 192.168.3.3).