100+ Real-Time CCNA Interview Questions and Answers [2025]

Networking Fundamentals

1. What would you do if a network device fails to connect to the network?

• Check physical connections
• Verify IP configuration
• Ping default gateway
• Review logs
  Device connectivity failures often stem from misconfigured IPs or loose cables. Checking connections and configurations ensures quick resolution, vital for CCNA certification scenarios requiring stable network operations.

2. How would you configure a static IP on a Cisco router?

Router>enable
Router#configure terminal
Router(config)#interface gigabitEthernet 0/0
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config-if)#no shutdown

Enter global configuration mode, set IP on the interface, and enable it. This assigns a static IP, ensuring reliable routing, a core CCNA skill for network setup.

3. Why would a network experience packet loss?

• Congested links
• Faulty cables
• Misconfigured QoS
• Check with ping
  Packet loss disrupts communication. Identifying congestion or hardware issues via diagnostics ensures stable networks, critical for CCNA certification interviews.

4. When would you use a crossover cable in a network?

Use crossover cables when:

• Connecting similar devices
• Example: switch-to-switch
• Direct communication needed
  Crossover cables enable direct device connections without a hub, essential for specific CCNA scenarios like legacy network setups.

5. Where would you check a Cisco device’s running configuration?

Router#show running-config

View configuration in CLI with show running-config. It displays active settings, crucial for troubleshooting, a key CCNA skill for network management.

6. Who would configure VLANs on a Cisco switch, and why?

• Network admins
• Segment traffic
• Enhance security
• Improve performance
  VLANs isolate traffic for efficiency and security. Admins configure them to optimize networks, a fundamental CCNA task for enterprise environments.

7. Which OSI layer handles IP addressing?

• Network Layer (Layer 3)
• Manages logical addressing
• Routes packets
  IP addressing at Layer 3 enables routing across networks, a core concept for CCNA certification and network design interviews.

8. What would you do if a Cisco switch port is down?

• Check cable connections
• Verify port status with show interface
• Enable port with no shutdown
• Inspect logs
  A down port halts traffic. Checking physical and logical settings resolves issues, ensuring uptime, a critical CCNA troubleshooting skill.

9. How would you verify connectivity between two Cisco devices?

Router#ping 192.168.1.2

Use ping to test reachability. Success confirms connectivity; failure indicates issues. This is a basic CCNA diagnostic tool for network validation.

10. Why would a network have high latency?

• Overloaded links
• Long routing paths
• Misconfigured QoS
• Monitor with traceroute
  High latency slows performance. Identifying and optimizing bottlenecks ensures efficient networks, a key focus for CCNA certification scenarios.

11. When would you use a default gateway in a network?

Use default gateway when:

• Devices need external access
• Routing to unknown networks
• Configured on hosts
  Default gateways enable internet access, a fundamental CCNA concept for network connectivity.

12. Where would you store Cisco device backups?

• TFTP server
• Flash memory
• External storage
• Use copy running-config tftp
  Backups ensure recovery from failures. Storing configurations securely is a critical CCNA practice for network reliability.

13. Who would use the Cisco IOS CLI, and for what purpose?

• Network engineers
• Configure devices
• Troubleshoot issues
• Monitor performance
  CLI enables precise device management, a core CCNA skill for configuring and maintaining Cisco networks.

14. Which protocol would you use for dynamic IP assignment?

• DHCP
• Assigns IPs automatically
• Reduces manual configuration
  DHCP streamlines IP management, essential for scalable networks, a key CCNA certification topic.

15. What would you do if a Cisco router fails to boot?

• Check boot image
• Verify flash memory
• Use show version
• Reload with reload
  Boot failures disrupt routing. Diagnosing hardware or software issues ensures recovery, vital for CCNA troubleshooting scenarios.

Routing

16. What would you do if a Cisco router drops packets?

• Check routing table with show ip route
• Verify ACLs
• Inspect interface errors
• Monitor with debug
  Packet drops indicate routing issues. Diagnosing tables and ACLs resolves problems, a critical CCNA skill for stable routing.

17. How would you configure OSPF on a Cisco router?

Router#configure terminal
Router(config)#router ospf 1
Router(config-router)#network 192.168.1.0 0.0.0.255 area 0

Enable OSPF, define networks, and assign areas. This ensures dynamic routing, a key CCNA skill for enterprise networks.

18. Why would a static route fail to work?

• Incorrect destination
• Wrong next-hop IP
• Check with show ip route
• Verify connectivity
  Static routes fail due to misconfiguration. Validating entries ensures reliable routing, essential for CCNA certification scenarios.

19. When would you use RIP over OSPF?

Use RIP when:

• Small networks
• Simple configuration needed
• Limited resources
  RIP suits small setups due to simplicity, but OSPF is preferred for scalability, a key CCNA routing concept.

20. Where would you check OSPF neighbor status?

Router#show ip ospf neighbor

Use show ip ospf neighbor in CLI. It verifies adjacency, critical for OSPF functionality and CCNA troubleshooting scenarios.

21. Who would configure BGP in a network, and why?

• Senior network engineers
• Manage external routing
• Ensure ISP connectivity
  BGP handles inter-domain routing, essential for large-scale networks, a key CCNA topic for advanced routing.

22. Which routing protocol would you use for a small office?

• RIP
• Simple setup
• Low resource usage
  RIP is ideal for small networks due to ease of configuration, a practical CCNA choice for basic routing.

23. What would you do if OSPF fails to form adjacencies?

• Check MTU settings
• Verify network types
• Inspect authentication
• Use debug ip ospf
  Adjacency failures disrupt routing. Debugging settings ensures OSPF functionality, a critical CCNA troubleshooting skill.

24. How would you configure a static route on a Cisco router?

Router#configure terminal
Router(config)#ip route 10.0.0.0 255.255.255.0 192.168.1.2

Define destination and next-hop. This ensures manual routing, a fundamental CCNA skill for network control.

25. Why would BGP neighbors fail to establish?

• Incorrect AS numbers
• Misconfigured peer IPs
• Check with show ip bgp
• Verify connectivity
  BGP failures disrupt external routing. Validating configurations ensures connectivity, essential for CCNA certification scenarios.

26. When would you use a floating static route?

Use floating static routes when:

• Backup path needed
• Primary route fails
• Higher administrative distance
  Floating routes provide redundancy, a key CCNA concept for reliable network design.

27. Where would you verify routing protocol status?

Router#show ip protocols

Use show ip protocols in CLI. It displays active protocols, critical for CCNA troubleshooting and routing validation.

28. Who would implement EIGRP in a Cisco network, and why?

• Network engineers
• Fast convergence
• Scalable routing
  EIGRP offers efficient routing for medium networks, a key CCNA skill for enterprise environments.

29. Which Cisco command would you use to debug routing issues?

• debug ip routing
• Monitors route changes
• Use cautiously
  Debugging identifies routing errors, ensuring stable networks, a critical CCNA troubleshooting tool.

30. What would you do if a route is missing from the routing table?

• Check protocol configuration
• Verify network statements
• Inspect redistribution
• Use show ip route
  Missing routes disrupt connectivity. Validating configurations ensures proper routing, essential for CCNA certification scenarios.

Switching

31. What would you do if a VLAN is not propagating across switches?

• Check VTP configuration
• Verify trunk links
• Inspect VTP domain
• Use show vtp status
  VLAN propagation failures isolate devices. Correcting VTP and trunks ensures connectivity, a key CCNA switching skill.

32. How would you configure a VLAN on a Cisco switch?

Switch#configure terminal
Switch(config)#vlan 10
Switch(config-vlan)#name SALES
Switch(config-vlan)#exit
Switch(config)#interface gigabitEthernet 0/1
Switch(config-if)#switchport mode access
Switch(config-if)#switchport access vlan 10

Create VLAN, name it, and assign to a port. This segments traffic, a fundamental CCNA switching task.

33. Why would a switch port drop frames?

• Speed/duplex mismatch
• Faulty cables
• Check with show interface
• Adjust settings
  Frame drops disrupt traffic. Correcting mismatches ensures reliable switching, critical for CCNA certification scenarios.

34. When would you use a trunk port in a Cisco switch?

Use trunk ports when:

• Connecting switches
• Carrying multiple VLANs
• Enabling inter-VLAN routing
  Trunk ports enable VLAN communication, a core CCNA concept for network segmentation.

35. Where would you verify VLAN assignments on a Cisco switch?

Switch#show vlan brief

Use show vlan brief in CLI. It lists VLANs and ports, essential for CCNA switching troubleshooting.

36. Who would configure Spanning Tree Protocol (STP) on a switch?

• Network admins
• Prevent loops
• Ensure redundancy
  STP avoids network loops, a critical CCNA skill for stable switch operations.

37. Which Cisco switch would you use for a small business?

• Catalyst 9200
• Cost-effective
• Supports basic features
  Catalyst 9200 suits small networks, providing affordable switching, a practical CCNA choice.

38. What would you do if a switch experiences broadcast storms?

• Enable storm control
• Check STP settings
• Use show spanning-tree
• Isolate source
  Broadcast storms overload networks. Storm control and STP ensure stability, vital for CCNA troubleshooting.

39. How would you configure a trunk port on a Cisco switch?

Switch#configure terminal
Switch(config)#interface gigabitEthernet 0/2
Switch(config-if)#switchport mode trunk
Switch(config-if)#switchport trunk allowed vlan 10,20

Set port to trunk mode and specify VLANs. This enables multi-VLAN traffic, a key CCNA switching skill.

40. Why would a Cisco switch fail to forward traffic?

• Port security enabled
• VLAN misconfiguration
• Check with show interface
• Verify settings
  Traffic failures isolate devices. Validating configurations ensures switching, essential for CCNA certification scenarios.

41. When would you use EtherChannel in a Cisco network?

Use EtherChannel when:

• Needing higher bandwidth
• Ensuring redundancy
• Connecting switches
  EtherChannel aggregates links, improving performance, a key CCNA concept for network scalability.

42. Where would you check STP status on a Cisco switch?

Switch#show spanning-tree

Use show spanning-tree in CLI. It displays STP details, critical for CCNA loop prevention and troubleshooting.

43. Who would configure port security on a Cisco switch, and why?

• Network admins
• Restrict unauthorized access
• Enhance security
  Port security limits device access, a core CCNA skill for secure network management.

44. Which Cisco command would you use to verify MAC address table?

• show mac address-table
• Lists device mappings
• Aids troubleshooting
  MAC address table verifies device connections, essential for CCNA switching diagnostics.

45. What would you do if a switch port is in err-disabled state?

• Check reason with show interfaces status
• Fix issue (e.g., port security)
• Re-enable with shutdown, no shutdown
  Err-disabled ports halt traffic. Resolving issues restores connectivity, a critical CCNA troubleshooting skill.

Security

46. What would you do if a Cisco router is under a DoS attack?

• Apply ACLs to filter traffic
• Enable rate limiting
• Monitor with show ip traffic
• Log events
  DoS attacks overwhelm devices. ACLs and monitoring mitigate threats, vital for CCNA security scenarios.

47. How would you configure an ACL on a Cisco router?

Router#configure terminal
Router(config)#access-list 101 permit tcp 192.168.1.0 0.0.0.255 any eq 80
Router(config)#interface gigabitEthernet 0/0
Router(config-if)#ip access-group 101 in

Create ACL, permit specific traffic, and apply to interface. This controls access, a key CCNA security skill.

48. Why would a Cisco device reject SSH connections?

• Missing SSH configuration
• Incorrect ACLs
• Check with show ip ssh
• Verify keys
  SSH failures prevent remote access. Validating settings ensures secure management, critical for CCNA certification.

49. When would you use NAT on a Cisco router?

Use NAT when:

• Conserving public IPs
• Connecting private networks
• Enhancing security
  NAT hides internal IPs, a core CCNA concept for network privacy and scalability.

50. Where would you configure firewall rules on a Cisco device?

Router#configure terminal
Router(config)#access-list 100 deny ip any 192.168.1.0 0.0.0.255
Router(config)#interface gigabitEthernet 0/0
Router(config-if)#ip access-group 100 in

Apply ACLs on interfaces. This filters traffic, ensuring security, a critical CCNA skill for network protection.

51. Who would implement VPNs on a Cisco network, and why?

• Network engineers
• Secure remote access
• Protect data
  VPNs encrypt connections, ensuring secure communication, a key CCNA topic for enterprise networks.

52. Which protocol would you use for secure management of Cisco devices?

• SSH
• Encrypts communication
• Replaces Telnet
  SSH ensures secure remote access, a fundamental CCNA practice for device management.

53. What would you do if unauthorized devices access a Cisco network?

• Enable port security
• Restrict MAC addresses
• Monitor with show port-security
• Log violations
  Unauthorized access risks security. Port security and monitoring protect networks, vital for CCNA scenarios.

54. How would you configure SSH on a Cisco router?

Router#configure terminal
Router(config)#hostname Router1
Router(config)#ip domain-name example.com
Router(config)#crypto key generate rsa
Router(config)#line vty 0 4
Router(config-line)#transport input ssh

Set hostname, domain, generate keys, and enable SSH. This secures remote access, a core CCNA skill.

55. Why would a Cisco firewall block legitimate traffic?

• Misconfigured rules
• Incorrect NAT settings
• Check with show access-list
• Adjust rules
  Blocked traffic disrupts services. Validating firewall settings ensures access, critical for CCNA security troubleshooting.

56. When would you use port security on a Cisco switch?

Use port security when:

• Limiting device access
• Preventing MAC spoofing
• Enhancing security
  Port security restricts unauthorized devices, a key CCNA practice for secure networks.

57. Where would you verify ACLs on a Cisco router?

Router#show access-lists

Use show access-lists in CLI. It displays active ACLs, essential for CCNA security troubleshooting and validation.

58. Who would configure AAA on a Cisco device, and why?

• Network admins
• Centralized authentication
• Enhance security
  AAA controls access, ensuring secure management, a critical CCNA skill for enterprise networks.

59. Which Cisco command would you use to monitor security events?

• show logging
• Displays system logs
• Tracks violations
  Logging monitors security events, essential for CCNA troubleshooting and network protection.

60. What would you do if a Cisco device’s ACL is too restrictive?

• Review with show access-lists
• Modify rules
• Test with ping
• Log changes
  Restrictive ACLs block legitimate traffic. Adjusting rules ensures access, a key CCNA security troubleshooting skill.

Troubleshooting

61. What would you do if a Cisco device loses connectivity?

• Check interfaces with show ip interface brief
• Verify cables
• Ping remote devices
• Review logs
  Connectivity loss isolates devices. Diagnosing interfaces and connections restores access, critical for CCNA troubleshooting.

62. How would you troubleshoot a Cisco switch with high CPU usage?

Switch#show processes cpu sorted

Check CPU with show processes cpu. Identify processes, reduce load, and monitor. This ensures switch performance, a key CCNA troubleshooting skill.

63. Why would a Cisco router fail to route traffic?

• Missing routes
• ACL blocking
• Check with show ip route
• Debug with debug ip packet
  Routing failures disrupt connectivity. Validating routes and ACLs ensures functionality, essential for CCNA certification.

64. When would you use debug commands in Cisco troubleshooting?

Use debug when:

• Diagnosing specific issues
• Monitoring real-time events
• Example: debug ip ospf
  Debugging provides insights, but use cautiously. It’s critical for CCNA troubleshooting scenarios.

65. Where would you check interface errors on a Cisco device?

Router#show interfaces

Use show interfaces in CLI. It displays errors like CRC or collisions, vital for CCNA troubleshooting.

66. Who would troubleshoot a Cisco network outage, and why?

• Network engineers
• Restore connectivity
• Ensure uptime
  Engineers diagnose outages to maintain services, a core CCNA responsibility in enterprise networks.

67. Which Cisco command would you use to verify interface status?

• show ip interface brief
• Lists interface states
• Aids diagnostics
  This command checks interface uptime, essential for CCNA troubleshooting and network validation.

68. What would you do if a Cisco device reboots unexpectedly?

• Check logs with show logging
• Verify power supply
• Inspect crashinfo
• Update IOS
  Unexpected reboots indicate issues. Diagnosing logs and hardware ensures stability, critical for CCNA scenarios.

69. How would you troubleshoot a VLAN connectivity issue?

Switch#show vlan brief
Switch#show interfaces trunk

Verify VLAN assignments and trunk status. Test with ping. This resolves connectivity, a key CCNA switching skill.

70. Why would a Cisco switch drop packets?

• Buffer overflow
• Misconfigured QoS
• Check with show interfaces
• Adjust settings
  Packet drops degrade performance. Diagnosing buffers ensures reliable switching, essential for CCNA troubleshooting.

71. When would you use traceroute in Cisco troubleshooting?

Use traceroute when:

• Identifying path issues
• Locating failures
• Testing reachability
  Traceroute pinpoints routing problems, a critical CCNA tool for network diagnostics.

72. Where would you check for Cisco device errors?

Router#show logging

Use show logging in CLI. It displays system errors, essential for CCNA troubleshooting and diagnostics.

73. Who would monitor Cisco network performance, and why?

• Network admins
• Ensure uptime
• Optimize resources
  Monitoring maintains performance, a key CCNA responsibility for reliable networks.

74. Which Cisco command would you use to verify NAT translations?

• show ip nat translations
• Lists active translations
• Aids troubleshooting
  NAT verification ensures address mapping, critical for CCNA security and connectivity.

75. What would you do if a Cisco device’s interface flaps?

• Check cables
• Verify speed/duplex
• Monitor with show interfaces
• Replace hardware
  Flapping disrupts connectivity. Diagnosing hardware and settings ensures stability, a CCNA troubleshooting skill.

Advanced Topics

76. What would you do if a Cisco device runs out of memory?

• Check with show memory
• Reduce processes
• Upgrade hardware
• Monitor logs
  Memory exhaustion crashes devices. Optimizing resources ensures stability, critical for CCNA advanced scenarios.

77. How would you configure PoE on a Cisco switch?

Switch#configure terminal
Switch(config)#interface gigabitEthernet 0/1
Switch(config-if)#power inline auto

Enable PoE on interfaces. This powers devices like IP phones, a key CCNA skill for modern networks.

78. Why would a Cisco device fail to sync with NTP?

• Incorrect NTP server
• Firewall blocking
• Check with show ntp status
• Verify connectivity
  NTP failures affect time accuracy. Validating servers ensures synchronization, essential for CCNA scenarios.

79. When would you use QoS in a Cisco network?

Use QoS when:

• Prioritizing traffic
• Managing bandwidth
• Ensuring performance
  QoS optimizes resource allocation, a critical CCNA concept for enterprise networks.

80. Where would you configure SNMP on a Cisco device?

Router#configure terminal
Router(config)#snmp-server community public RO
Router(config)#snmp-server host 192.168.1.100 public

Configure SNMP in global mode. This enables monitoring, essential for CCNA network management.

81. Who would implement SD-WAN in a Cisco network, and why?

• Network architects
• Optimize WAN
• Enhance scalability
  SD-WAN improves connectivity, a key CCNA topic for modern enterprise networks.

82. Which Cisco feature would you use for network automation?

• Cisco DNA Center
• Automates configuration
• Simplifies management
  DNA Center streamlines operations, a critical CCNA skill for automated networks.

83. What would you do if a Cisco device’s IOS upgrade fails?

• Verify image integrity
• Check flash space
• Use show version
• Retry upgrade
  Failed upgrades disrupt devices. Validating images ensures success, critical for CCNA maintenance.

84. How would you configure HSRP on a Cisco router?

Router#configure terminal
Router(config)#interface gigabitEthernet 0/0
Router(config-if)#standby 1 ip 192.168.1.254
Router(config-if)#standby 1 priority 110

Set virtual IP and priority. HSRP ensures redundancy, a key CCNA skill for high availability.

85. Why would a Cisco device fail to authenticate users?

• Incorrect AAA settings
• Misconfigured RADIUS
• Check with show aaa servers
• Verify credentials
  Authentication failures block access. Validating settings ensures security, essential for CCNA scenarios.

86. When would you use VRF in a Cisco network?

Use VRF when:

• Segmenting routing tables
• Isolating networks
• Enhancing security
  VRF enables logical separation, a key CCNA concept for complex networks.

87. Where would you verify Cisco device performance metrics?

Router#show processes cpu
Router#show memory

Use CLI commands to check CPU and memory. This monitors performance, critical for CCNA troubleshooting.

88. Who would configure multicast in a Cisco network, and why?

• Network engineers
• Efficient data delivery
• Support streaming
  Multicast optimizes bandwidth, a key CCNA skill for multimedia networks.

89. Which Cisco command would you use to verify IP SLA?

• show ip sla statistics
• Monitors performance
• Tracks metrics
  IP SLA ensures service quality, essential for CCNA performance monitoring.

90. What would you do if a Cisco device’s VPN tunnel fails?

• Check encryption settings
• Verify peer IPs
• Debug with debug crypto
• Monitor logs
  VPN failures disrupt connectivity. Diagnosing settings ensures secure tunnels, critical for CCNA scenarios.

Wireless and Emerging Technologies

91. What would you do if a Cisco wireless AP fails to broadcast SSID?

• Check SSID configuration
• Verify radio status
• Use show ap config
• Restart AP
  SSID failures prevent connections. Validating settings restores access, a key CCNA wireless skill.

92. How would you configure a Cisco wireless LAN controller?

WLC#configure
WLC(config)#wlan create 1 MYWLAN
WLC(config-wlan)#ssid MYWLAN
WLC(config-wlan)#security wpa2

Create WLAN, set SSID, and enable security. This ensures wireless access, a core CCNA skill.

93. Why would a Cisco wireless network have poor signal quality?

• Interference
• Incorrect antenna placement
• Check with show wireless
• Adjust settings
  Poor signals degrade performance. Optimizing placement ensures reliability, essential for CCNA wireless scenarios.

94. When would you use a Cisco Meraki device in a network?

Use Meraki when:

• Cloud management needed
• Simplified deployment
• Scalable networks
  Meraki streamlines wireless management, a practical CCNA choice for modern networks.

95. Where would you verify wireless client connections?

WLC#show client summary

Use show client summary on WLC. It lists connected devices, critical for CCNA wireless troubleshooting.

96. Who would configure Cisco DNA Center, and why?

• Network architects
• Automate networks
• Monitor performance
  DNA Center simplifies management, a key CCNA skill for advanced networks.

97. Which protocol would you use for wireless security?

• WPA3
• Strong encryption
• Replaces WPA2
  WPA3 ensures secure wireless access, a critical CCNA topic for modern networks.

98. What would you do if a Cisco AP fails to join a controller?

• Check IP configuration
• Verify CAPWAP
• Use debug capwap
• Monitor logs
  AP failures disrupt wireless. Diagnosing settings ensures connectivity, vital for CCNA scenarios.

99. How would you configure a Cisco switch for VoIP phones?

Switch#configure terminal
Switch(config)#interface gigabitEthernet 0/1
Switch(config-if)#switchport voice vlan 20
Switch(config-if)#power inline auto

Set voice VLAN and PoE. This supports VoIP, a key CCNA skill for unified communications.

100. Why would a Cisco wireless network drop clients?

• Weak signal
• Overloaded AP
• Check with show ap status
• Optimize channels
  Client drops disrupt access. Optimizing APs ensures reliability, essential for CCNA wireless scenarios.

101. When would you use Cisco SD-Access in a network?

Use SD-Access when:

• Automating fabric
• Enhancing security
• Simplifying management
  SD-Access streamlines enterprise networks, a key CCNA topic for modern deployments.

Tips to Ace CCNA Interviews

• Practice CLI commands on Packet Tracer
• Build labs for routing, switching
• Master troubleshooting with show, debug
• Understand OSI, TCP/IP models
• Review Cisco documentation
• Explain solutions clearly, blending technical depth and simplicity