CCNA Interview Questions and Answers: A Study Sheet You Can Print

Key takeaways

• This page replaces a PDF: use your browser's print option to save it as one.
• Interviewers test whether you can explain and troubleshoot, not recite definitions.
• Core areas are OSI, subnetting, VLANs, STP, OSPF, ACLs, NAT, DHCP and basic troubleshooting.
• CCNA 200-301 is a single exam, so questions follow its blueprint across networking, security and automation basics.
• Practise every answer on Packet Tracer or a lab, and be ready to type the commands.
• Never claim experience you do not have. Say what you built in a lab and what you would check first.

How should you use this page instead of a PDF?

Many people search for a "CCNA interview questions PDF" hoping to memorise a file. Memorising does not work well, because interviewers follow up with "what would you check first?" This page gives short, accurate answers you can read, then practise in a lab. To keep a copy, use your browser's print dialogue and choose "Save as PDF".

What do interviewers ask about the OSI and TCP/IP models?

Q: Name the OSI layers and one device or protocol at each. Physical (cables, hubs), Data Link (switches, MAC addresses, Ethernet), Network (routers, IP), Transport (TCP, UDP), Session, Presentation, Application (HTTP, DNS). A good answer adds where you troubleshoot first: check the physical link, then VLAN and addressing, then routing, then ports.

Q: How do TCP and UDP differ? TCP is connection-oriented, with a three-way handshake, acknowledgements and retransmission. UDP is connectionless and has less overhead, which suits DNS queries and voice. Choose by whether reliability or low delay matters more.

What subnetting questions come up?

Q: How many usable hosts are in a /26? A /26 has 6 host bits, so 2 to the power 6 is 64 addresses, minus network and broadcast leaves 62 usable. Practise by hand: given 192.168.10.77/26, the network is 192.168.10.64, the broadcast is 192.168.10.127 and the usable range is.65 to.126.

Q: What is the difference between a public and private IPv4 address? Private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are not routed on the internet and need NAT to reach it. Public addresses are globally unique.

Which switching questions are common?

• VLAN: a logical broadcast domain on a switch, used to separate traffic by function. Trunk links carry several VLANs using 802.1Q tags.
• Spanning Tree Protocol: prevents Layer 2 loops by blocking redundant paths. Know root bridge election (lowest bridge priority, then lowest MAC) and that Rapid PVST+ converges faster than the original.
• EtherChannel: bundles links for bandwidth and redundancy, using LACP or PAgP.
• Port security: limits MAC addresses on a port to stop rogue devices.

Which routing questions are common?

Q: How does OSPF work in brief? It is a link-state protocol. Routers form neighbours, exchange link-state advertisements, build the same topology database and run the SPF algorithm to choose the lowest cost path. Areas reduce database size, with Area 0 as the backbone. Expect to explain the DR and BDR on multi-access networks.

Q: What is administrative distance? It ranks the trustworthiness of route sources when several protocols offer a route to the same prefix. Lower wins: connected 0, static 1, EIGRP 90, OSPF 110, RIP 120. Metric is then used within one protocol.

Q: Static vs dynamic routing? Static is simple and predictable for small or stub networks. Dynamic adapts to change but uses CPU, memory and bandwidth.

What about ACLs and NAT?

Q: Standard vs extended ACL? Standard ACLs match source address only and are placed close to the destination. Extended ACLs match source, destination, protocol and ports and are placed close to the source. Every ACL ends with an implicit deny.

Q: Explain static NAT, dynamic NAT and PAT. Static maps one inside address to one outside address. Dynamic uses a pool. PAT (overload) maps many inside addresses to one outside address using different port numbers.

Which troubleshooting scenarios should you rehearse?

How do you answer if you have no job experience?

Be honest. Describe a lab you built, such as three VLANs, inter-VLAN routing and OSPF in Packet Tracer, what failed, and how you fixed it. Interviewers value a clear troubleshooting method more than invented project claims. Also know what changed with the exam itself: CCNA 200-301 is one combined exam, and the older separate CCNA tracks were retired in February 2020, so be wary of any question set that refers to them.

What should a one-week revision plan look like?

1. Day 1: OSI, TCP/IP, TCP vs UDP, common ports.
2. Day 2: Subnetting drills, ten problems by hand.
3. Day 3: VLANs, trunking, STP, EtherChannel in a lab.
4. Day 4: OSPF and static routes, then administrative distance.
5. Day 5: ACLs, NAT and DHCP.
6. Day 6: Troubleshooting drills from the table above.
7. Day 7: Mock interview: explain three answers aloud, with a commands cheat sheet.

For more question sets, read top CCNA interview questions, CCNA technical interview questions and CCNA exam preparation questions. Cisco's own CCNA exam page lists the current blueprint.

Next steps

To practise these answers on real devices and simulators, see WebAsha's CCNA training course.

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