CCNA IP and ACL interview questions often combine traffic filtering, address translation, and WAN terminology. These answers explain the concepts and the commands used to verify them.
For guided practice, use our extended ACL configuration lab and the Cisco 200-301 Premium PDF with the latest available questions and answers.
What is an access control list?
An ACL is an ordered set of permit and deny statements. Cisco devices evaluate entries from top to bottom and stop at the first match. An implicit deny exists at the end.
What is a standard ACL?
A standard IPv4 ACL normally matches only the source IPv4 address. It is generally placed close to the destination so it does not block more traffic than intended.
What is an extended ACL?
An extended ACL can match protocol, source, destination, and TCP or UDP port information. It is generally placed close to the source.
What is a wildcard mask?
In an ACL wildcard mask, a zero bit means the corresponding address bit must match, while a one bit means it is ignored.
Can a numbered ACL be edited?
Modern IOS supports sequence numbers and named ACL editing methods. The exact workflow depends on software version and configuration style.
What is NAT?
Network Address Translation changes IP addressing information as traffic crosses a device. It can map private inside addresses to public addresses.
What is PAT?
Port Address Translation lets multiple inside hosts share one public IPv4 address by distinguishing sessions with transport-layer port numbers.
What are DTE and DCE?
In a traditional serial connection, DCE provides clocking while DTE receives it. In a lab, the DCE side may require a configured clock rate.
What is PPP?
Point-to-Point Protocol provides Layer 2 encapsulation for point-to-point links and supports features such as authentication.
Verification Commands
Use show access-lists, show ip interface, show ip nat translations, show interfaces serial, and controlled ping or application tests.