Cisco CCNA NAT for IPv4 4

Question 1

A company wants external internet users to reach an internal web server at 10.0.0.5 via the public IP 198.51.100.10. Which NAT type should be used?

Accepted Answer

Static NAT

Answer

Static NAT creates a permanent one-to-one mapping between a private IP and a public IP, allowing inbound connections to reach internal servers predictably.

Question 2

What happens to the NAT translation table entry when an idle TCP session times out?

Accepted Answer

The entry is removed after the NAT timeout expires

Answer

Cisco IOS removes idle dynamic NAT/PAT entries after a configurable timeout (default 24 hours for TCP, 5 minutes for UDP) to reclaim table space.

Question 3

Which IOS command defines a NAT pool named MYPOOL with addresses 198.51.100.1 through 198.51.100.10 and a /28 mask?

Accepted Answer

ip nat pool MYPOOL 198.51.100.1 198.51.100.10 netmask 255.255.255.240

Answer

The correct syntax is 'ip nat pool [name] [start-ip] [end-ip] netmask [mask]' — prefix-length is an alternative but 'netmask' is the traditional keyword.

Question 4

Which Cisco IOS command links an access list to a NAT pool for dynamic translation?

Accepted Answer

ip nat inside source list 10 pool MYPOOL

Answer

'ip nat inside source list [acl] pool [pool-name]' ties ACL-matched inside source addresses to the specified pool for dynamic NAT.

Question 5

NAT is often criticized for which networking principle violation?

Accepted Answer

It violates end-to-end connectivity by modifying IP headers in transit

Answer

NAT violates the end-to-end principle of IP networking because it modifies source/destination addresses in packet headers, breaking transparency between endpoints.

Cisco CCNA Practice Test

Cisco CCNA Practice Test

Cisco CCNA NAT for IPv4 4