500+ CCNA Interview Questions with Answer 2026

Detailed Exam Domain Coverage

This practice test bank is structured precisely around the core domains encountered in modern CCNA interviews, technical assessments, and professional networking certifications:

• Networking Fundamentals (20%)

  • Topics Covered: Detailed mechanics of the OSI model and TCP/IP model, data encapsulation and de-encapsulation processes, characteristics of MAC addresses, and foundational IP addressing properties.

• IP Addressing & Subnetting (15%)

  • Topics Covered: Advanced IPv4 addressing, custom subnetting architectures, Variable Length Subnet Masking (VLSM) optimization, and Classless Inter-Domain Routing (CIDR) block allocation.

• Routing & Switching (25%)

  • Topics Covered: Core routing protocol operations (OSPF, EIGRP, RIPv2), administrative distance configurations, static routing mechanics, and Spanning Tree Protocol (STP) topologies.

• Network Security (15%)

  • Topics Covered: Deploying standard and extended Access Control Lists (ACLs), Network Address Translation (NAT) deployment, firewall integration, and secure DHCP and DNS configurations.

• Troubleshooting Techniques (10%)

  • Topics Covered: Layered troubleshooting methodologies, interface debugging, live packet captures, deep protocol analysis, and active network monitoring infrastructure.

• WAN & LAN Technologies (5%)

  • Topics Covered: Local area network infrastructure, enterprise wide area network architectures, Ethernet standards, wireless networking mechanics, and Wi-Fi deployment protocols.

• IPv6 Essentials (5%)

  • Topics Covered: Structure of IPv6 addressing, stateless and stateful address configuration, IPv6 subnetting strategies, native routing protocols, and IPv6 transition mechanisms.

• Network Management (5%)

  • Topics Covered: Enterprise management tools, Simple Network Management Protocol (SNMP) structures, system logs (Syslog), NetFlow traffic analysis, and diagnostic network utilities.

Course Description

Securing a position as a network professional requires more than just memorizing basic command syntax or configuration guides. Technical interviewers look for solid diagnostic intuition, deep protocol knowledge, and the ability to troubleshoot complex, real-world network anomalies on production hardware. I engineered this comprehensive practice question bank to bridge the gap between basic theory and the challenging, situational scenarios frequently presented during intermediate and advanced technical interview rounds.

With 550 high-quality, unique questions, this course accurately simulates the technical depth required to clear technical screens and deep-dive design discussions for roles like Network Engineer, CCNA Expert, and Junior Network Engineer. Every single question includes a comprehensive breakdown explaining the exact architectural and protocol rules that make the correct answer right, while breaking down why the alternative choices fail under production conditions.

Instead of generic, high-level summaries, you will analyze actual scenarios dealing with suboptimal routing paths, broken spanning tree topologies, misconfigured access control lists, and nested subnetting schemes. By working through these rigorous, targeted assessments, you will learn to dissect complex problems systematically, giving you the clarity and confidence needed to articulate elite technical answers during your actual interviews.

Sample Practice Questions Preview

Question 1: Routing & Switching (OSPF Neighbor Adjacencies)

Two multi-layer switches running OSPF are connected directly via a GigabitEthernet link configured as a broadcast network type. During a configuration audit, an engineer notices that both switches remain permanently stuck in the "2-WAY" neighbor state rather than advancing to "FULL." What is the root cause of this behavior, and how should it be handled?

• A) There is a mismatch in the configured OSPF Hello or Dead interval timers on the connecting interfaces.

  • Why Incorrect: If there is a mismatch in Hello or Dead intervals, the routers will refuse to form a neighbor relationship at all. They will drop out of the process entirely and never even reach the 2-WAY state.

• B) The maximum transmission unit (MTU) sizes on the connecting local interfaces do not match.

  • Why Incorrect: Mismatched MTU sizes allow routers to form an initial relationship, but they will become permanently stuck in the EXSTART or EXCHANGE state during the Database Description (DBD) packet exchange, not the 2-WAY state.

• C) Both switches have been configured with an OSPF priority of 0, making them both Designated Router Observers (DROTHERs) on a multi-access segment.

  • Why Correct: In an OSPF broadcast network, routers that are neither the Designated Router (DR) nor the Backup Designated Router (BDR) are classified as DROTHERs. DROTHERs form full adjacencies only with the DR and BDR. Between two DROTHERs, staying in the 2-WAY state is standard, healthy behavior designed to limit unnecessary routing table synchronization overhead.

• D) The configured OSPF process ID numbers fail to match on both sides of the connecting link.

  • Why Incorrect: OSPF process IDs are locally significant to the individual router. They do not need to match between neighboring devices to establish a fully functional OSPF adjacency.

• E) One interface is configured to use clear-text authentication while the opposing peer interface uses MD5 cryptographic authentication.

  • Why Incorrect: Authentication type or key mismatches cause the routers to reject incoming OSPF packets completely. The neighbor relationship will fail to initialize and will never establish a 2-WAY state.

• F) The subnet masks applied to the connecting interfaces are mismatched, stopping data link packet propagation.

  • Why Incorrect: For broadcast networks, OSPF requires identical subnet masks to form an adjacency. A mask mismatch causes the routers to ignore Hello packets, failing the initialization phase entirely.

Question 2: IP Addressing & Subnetting (VLSM Design)

An enterprise infrastructure plan requires a network administrator to divide the private block 172.16.40.0/24 using Variable Length Subnet Masking (VLSM) to host three distinct corporate subnets. The Engineering group needs up to 60 valid host addresses, the Operations group needs up to 28 valid host addresses, and the Support group needs up to 14 valid host addresses. Which allocation strategy represents the most efficient use of address space without any overlapping?

• A) Engineering: 172.16.40.0/26, Operations: 172.16.40.64/27, Support: 172.16.40.96/28

  • Why Correct: This distribution fits the host requirements perfectly without wasting address space. Engineering requires 60 hosts, which fits inside a /26 mask (62 usable IPs, range .0 to .63). Operations requires 28 hosts, fitting inside a /27 mask (30 usable IPs, range .64 to .95). Support requires 14 hosts, fitting inside a /28 mask (14 usable IPs, range .96 to .111). All subnets sit next to each other cleanly with no overlap.

• B) Engineering: 172.16.40.0/25, Operations: 172.16.40.128/26, Support: 172.16.40.192/27

  • Why Incorrect: While this plan avoids overlap, it wastes a massive number of unassigned IP addresses. Using a /25 for 60 hosts, a /26 for 28 hosts, and a /27 for 14 hosts allocates double the required space for every department, breaking the rule of maximum efficiency.

• C) Engineering: 172.16.40.0/26, Operations: 172.16.40.32/27, Support: 172.16.40.64/28

  • Why Incorrect: This layout creates an immediate address overlap. The Engineering network (/26) runs from 172.16.40.0 through 172.16.40.63. The Operations network starting at .32 directly collides with the middle of the Engineering block, causing severe routing errors.

• D) Engineering: 172.16.40.0/26, Operations: 172.16.40.64/26, Support: 172.16.40.128/26

  • Why Incorrect: This structure applies a uniform /26 mask to all subnets. While it fits the Engineering group, it wastes valuable space in the Operations and Support networks by provisioning 62 usable addresses where only 28 and 14 are required, ignoring the benefits of VLSM.

• E) Engineering: 172.16.40.0/27, Operations: 172.16.40.32/28, Support: 172.16.40.48/29

  • Why Incorrect: These subnets are entirely too small to host the required infrastructure. A /27 provides only 30 usable hosts, which fails Engineering (60 needed). A /28 provides 14 usable hosts, failing Operations (28 needed). A /29 provides only 6 usable hosts, failing Support (14 needed).

• F) Engineering: 172.16.40.0/24, Operations: 172.16.41.0/25, Support: 172.16.42.0/26

  • Why Incorrect: This strategy uses three entirely separate classful /24 blocks (40.0, 41.0, and 42.0) instead of subnetting within the requested 172.16.40.0/24 boundary, completely violating the constraints of the prompt.

Question 3: Network Security (Extended Access Control Lists)

An engineer deploys an extended Access Control List (ACL) on an inbound internet-facing interface of a boundary router to prevent external attackers from reaching sensitive internal servers. Right after applying the ACL, internal corporate employees discover they can no longer reach external public web servers or browse internet websites. What configuration mistake caused this breakdown?

• A) The extended ACL lacks an explicit statement permitting return traffic, meaning the implicit deny all rule at the end is dropping inbound web replies.

  • Why Correct: Cisco ACLs contain an invisible, mandatory "deny ip any any" statement at the very end of the list. When internal users create outbound web connections, the return traffic from the public servers hits the inbound interface. If the ACL does not explicitly permit this returning traffic, it triggers the implicit deny and blocks the connection.

• B) Extended ACLs are required to be placed as close to the traffic source as possible, meaning applying it to the internet interface dropped all local outbound packets.

  • Why Incorrect: Extended ACLs should be placed as close to the traffic source as possible when filtering internal traffic to save bandwidth. However, for traffic coming from the internet, the internet interface is the closest entry point. The placement itself is correct; the rule definitions inside are flawed.

• C) The configuration used the incorrect port number, blocking UDP port 53 traffic instead of targeting standard TCP port 80 traffic.

  • Why Incorrect: Blocking UDP port 53 would cripple DNS resolution rather than web server access directly. Furthermore, if a rule simply had a wrong port matching error for inbound tracking, it would not explain the total block caused by the implicit deny on all general TCP responses.

• D) Applying an extended access list to an interface automatically wipes out the active dynamic Network Address Translation (NAT) translation tables.

  • Why Incorrect: Applying an ACL does not delete or clear the NAT translation table. NAT and ACLs operate independently within the Cisco IOS architecture, though they can reference the same traffic streams.

• E) The engineer mistakenly applied a standard ACL instead of an extended ACL, which automatically discards traffic based only on destination paths.

  • Why Incorrect: Standard ACLs filter traffic based only on the source IP address, not the destination. If a standard ACL were placed on the inbound internet interface, it would incorrectly filter traffic based on external source IPs, not destination variables.

• F) The configuration overwhelmed the available router NVRAM, causing an execution panic that shut down the physical interface links.

  • Why Incorrect: Access control lists are parsed and stored in active RAM and applied via hardware (TCAM) or software switching paths. An execution format error will not run out of NVRAM or cause a hardware link-down condition on physical interfaces.

• Welcome to the Interview Questions Tests to help you prepare for your CCNA Interview Questions.

• You can retake the exams as many times as you want

• This is a huge original question bank

• You get support from instructors if you have questions

• Each question has a detailed explanation

• Mobile-compatible with the Udemy app

I hope that by now you're convinced! And there are a lot more questions inside the course.