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CCNA - ACLs and NAT Configuration

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Question 1

In Cisco NAT terminology, the **inside local** address is the [[blank1]] IP address of the internal host before translation.

Explanation

Cisco defines four NAT address types:

- Inside local – the private IP of the inside host (pre-translation)

- Inside global – the public IP representing the inside host (post-translation, as seen from outside)

- Outside local – how an outside host's IP appears inside the network

- Outside global – the actual public IP of the outside host

Question 2

**True or False:** PAT (Port Address Translation) allows multiple internal hosts to share a single public IP address by using unique port numbers to track connections.

Answer choices

  • A. True (Correct)

  • B. False

Explanation

PAT (also called NAT Overload) maps multiple private IPs to one public IP by assigning unique source port numbers to each session. The NAT table tracks these port mappings to route return traffic to the correct internal host. This is the dominant form of NAT used in SOHO and enterprise environments.

Question 3

An ACL is applied to an interface with the command `ip access-group 101 in`. What does the keyword **"in"** specify?

Answer choices

  • A. Traffic exiting the interface toward the network

  • B. Traffic entering the interface from the network (Correct)

  • C. Traffic entering the router's management plane

  • D. Traffic going into the routing table

Explanation

"in" filters packets that are arriving on that interface (entering the router). "out" filters packets that are leaving via that interface. You can apply one ACL in each direction per interface per protocol.

Question 4

**NAT64** is primarily used to solve which networking problem?

Answer choices

  • A. Translating private RFC 1918 addresses to public addresses

  • B. Allowing IPv6-only hosts to communicate with IPv4-only servers (Correct)

  • C. Encrypting traffic between NAT boundaries

  • D. Extending the range of standard ACLs to 32-bit prefixes

Explanation

NAT64 enables communication between IPv6 and IPv4 networks. As the internet transitions to IPv6, NAT64 (combined with DNS64) allows IPv6-only clients to reach IPv4-only servers by translating packet headers at a gateway. This is a critical transition technology and appears on CCNA exams.

Question 5

Which wildcard mask correctly matches the subnet **10.10.0.0 /22**?

Answer choices

  • A. 0.0.3.255 (Correct)

  • B. 0.0.255.255

  • C. 255.255.252.0

  • D. 0.0.0.255

Explanation

A /22 subnet has a subnet mask of 255.255.252.0. The wildcard mask is the bitwise inverse: 0.0.3.255. This matches any IP address in the range 10.10.0.0–10.10.3.255, which is the full /22 block.