NAT (Network Address Translation) is a router function that rewrites the IP addresses in packet headers as packets pass between two networks, most often swapping private inside addresses for public ones. The router records each mapping in a translation table so that return traffic can be translated back.
In simple terms: Your office uses private addresses that the internet can't route. NAT lets the router swap them for a public address on the way out and swap them back on the way in.
Ten questions on the whole course. They use the same office as the lessons: PCs in 192.168.10.0/24, R1 with Gi0/0 inside and Gi0/1 outside (203.0.113.2), and a server at 198.51.100.10. If you get one wrong, go back to the lesson named in the explanation.
Predict · scenario 1
1. Which of these addresses is private (RFC 1918)?
Predict · scenario 2
2. PC1 is 192.168.10.11 and appears on the internet as 203.0.113.2. What is 203.0.113.2 called?
Predict · scenario 3
3. Which command marks Gi0/1 as the side facing the ISP?
Predict · scenario 4
4. Which kind of NAT lets someone on the internet start a connection to Web1?
Predict · scenario 5
5. In dynamic NAT, what is the job of 'access-list 1 permit 192.168.10.0 0.0.0.255'?
Predict · scenario 6
6. A dynamic NAT pool has 4 addresses, all in use. What happens to a fifth host?
Predict · scenario 7
7. Which command gives all office PCs internet access through Gi0/1's address?
Predict · scenario 8
8. In a PAT table, two rows both show inside global 203.0.113.2. What keeps them apart?
Predict · scenario 9
9. show ip nat statistics lists the office interface under 'Outside interfaces'. What is the effect?
Predict · scenario 10
10. R1's static NAT for Web1 (203.0.113.21) is correct, but outside users can't reach the site and no tcp rows ever appear. Which is the most likely cause?