Chapter 5 – NAT for IPv4
Study Guide
After completion of this chapter, you should be able to:
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Describe NAT characteristics.
Describe the benefits and drawbacks of NAT.
Configure static NAT using the CLI.
Configure dynamic NAT using the CLI.
Configure PAT using the CLI.
Configure port forwarding using the CLI.
Configure NAT64.
Use show commands to verify NAT operation.
1. What is the main purpose of NAT and how is it accomplished?
To conserve IP addresses by translating internal Private addresses into a public address that can be
used on the internet.
2. What role does a router play in NAT translations?
The NAT-enabled router translates the internal IPv4 address of the device to a public address from the
NAT pool.
3. Define the following NAT terms:
a. Inside Local Address – the address of the source as seen from inside the network
b. Inside Global Address – the address of the source as seen from the outside network
c. Outside Global Address – the address of the destination as seen from the outside network
d. Outside Local Address – the address of the destination as seen from the inside network
4. Complete Activity 5.1.1.6 – Identify the NAT Terminology
5. When would Static NAT need to be used?
For web servers or devices that must have a consistent address that is accessible from the Internet.
6. How is an address translated when using Dynamic NAT?
It uses a pool of public addresses and assigns them on a first-come, first-served basis.
7. How does PAT function differently from NAT, and what does it use to keep track of translations?
It maps multiple private addresses to a single public address by adding unique source port numbers to the inside
global address to distinguish between translations.
8. What are some disadvantages of NAT?
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Performance is degraded
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End-to-end functionality is degraded and IP traceability is lost
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Tunneling becomes more complicated
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Initiating TCP connections can be disrupted
9. What are the two basic steps in configuring static NAT translations?
Step 1: create a mapping between the inside local address and the inside global address.
Step 2: configure the interfaces that are participating in the translation as inside or outside relative to NAT.
10. When using Dynamic NAT, what happens when all the addresses in the pool have been used?
A device must wait for an available address before it can access the outside network.
11. What are the 5 steps in configuring Dynamic NAT?
a. Step 1 – Define a pool of global addresses to be used for translation
b. Step 2 – configure a standard ACL permitting the addresses that should be translated
c. Step 3 – bind the pool to the ACL
d. Step 4 – identify the inside interface
e. Step 5 – identify the outside interface
12. What keyword differentiates a PAT configuration from a NAT configuration? Overload
13. How can you use the command “show ip nat translations” to determine if you are running NAT or PAT?
PAT is being used when the Inside Global address is the same for all the translations.
14. Complete Activity 5.2.3.5 – Identify the Address Information at Each Hop
15. How can Port Forwarding be used to overcome NAT issues?
It forwards traffic addressed to a specific network port from one network node to another,
16. What are some characteristics of IPv6 Unique Local Addresses (ULA)?
Allows sites to be combined or privately interconnected, without creating any address conflicts or requiring
renumbering of interfaces that use these prefixes.
Independent of any ISP and can be used for communications within a site without having any Internet
connectivity.
Not routable across the Internet, however, if accidentally leaked by routing or DNS, there is not conflict with
other addresses.