CCNA – NAT PAT Questions

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

Question 1

Explanation

With static NAT, translations exist in the NAT translation table as soon as you configure static NAT command(s), and they remain in the translation table until you delete the static NAT command(s).

With dynamic NAT, translations do not exist in the NAT table until the router receives traffic that requires translation. Dynamic translations have a timeout period after which they are purged from the translation table.

-> A is correct.

Because static NAT translations are always present in the NAT table so outside hosts can initiate the connection without being dropped -> B is correct.

Static translations can not be configured with access lists. To configure static NAT, we only need to specify source IP, NAT IP, inside interface & outside interface.

-> C is not correct.

We have to specify which is the inside and outside interface -> D is not correct.

For your information, below is an example of configuring static NAT:

R0(config)#int f0/0
R0(config-if)#ip nat inside

R0(config-if)#int f0/1
R0(config-if)#ip nat outside

R0(config)#ip nat inside source static 10.0.0.1 200.0.0.2

(Reference: http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093f31.shtml)

Question 2

Explanation

By not reveal the internal IP addresses, NAT adds some security to the inside network -> A is correct.

NAT has to modify the source IP addresses in the packets -> B is not correct.

Connection from the outside to a network through “NAT” is more difficult than a normal network because IP addresses of inside hosts are hidden -> C is not correct.

In order for IPsec to work with NAT we need to allow additional protocols, including Internet Key Exchange (IKE), Encapsulating Security Payload (ESP) and Authentication Header (AH) -> more complex -> D is not correct.

By allocating specific public IP addresses to inside hosts, NAT eliminates the need to re-address the inside hosts -> E is correct.

NAT does conserve addresses but not through host MAC-level multiplexing. It conserves addresses by allowing many private IP addresses to use the same public IP address to go to the Internet -> F is not correct.

Question 3

Explanation

The “list 1″ refers to the access-list number 1.