2.1 Network Address Translation

Question 1

Why is NAT necessary for IPv4 networks?

Answer 1

Because IPv4 supports only 4.29 billion addresses, NAT allows many private devices to share a limited number of public IP addresses.

Transcript: “IP version 4 only supports 4.29 billion addresses… we have completely exhausted our list…” (0:13–0:22)

Question 2

What is Network Address Translation?

Answer 2

NAT is a process that allows private IP addresses to be translated into public IPs so devices can communicate over the Internet.

Transcript: “The way that we’re able to make this work is through a technology known as network address translation, or NAT.” (0:36–0:42)

Question 3

What is the purpose of RFC 1918?

Answer 3

RFC 1918 defines the reserved private IP address ranges that are not routable on the public Internet.

Transcript: “RFC 1918… defines these different ranges of private IP addresses… not routable on the public internet.” (1:07–1:22)

Question 4

What are the three main private IP address ranges defined by RFC 1918?

Answer 4

10.0.0.0 - 10.255.255.255

172.16.0.0 to 172.31.255.255

192.168.0.0 to 192.168.255.255

Transcript: (1:36–2:11)

Question 5

How does NAT allow a private IP to communicate with a public server?

Answer 5

It replaces the private source IP with a public IP before sending the packet and reverses the process for return traffic.

Transcript: “This router will change or translate that address… now we have a public IP address…” (3:00–3:27)

Question 6

What is Port Address Translation (PAT) also known as?

Answer 6

PAT is also known as NAT Overload. It allows many private devices to share a single public IP using unique port numbers.

Transcript: “Using a different form of network address translation called NAT overload, or port address translation, or PAT.” (4:40–4:48)

Question 7

How does PAT differ from standard NAT?

Answer 7

PAT maps multiple private IPs to a single public IP using different port numbers to differentiate each session.

Transcript: “Because we’re translating both the network address and the port number… other devices on this network could use the same public IP address.” (5:50–6:00)

Question 8

Why is PAT more efficient than standard NAT?

Answer 8

PAT allow multiple devices to use a single public IP by assigning unique port numbers, conserving public IPs.

Transcript: “We can now have many people on the inside of our network communicating externally… all using the same public IP address.” (6:44–6:52)