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Network Engineering > Interview Questions > Flashcards

Interview Questions Flashcards

1
Q

What steps would you take if a user reports no internet connectivity?

A

Check the physical connection, verify IP settings, test connectivity with ping, check for DHCP issues, and ensure the gateway is reachable.

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2
Q

How do you troubleshoot a failed ping test to a specific server?

A

Verify server availability, check DNS resolution, ensure correct routing, and inspect firewalls for blocked ICMP.

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3
Q

How do you resolve duplicate IP address conflicts?

A

Identify conflicting devices using arp -a, manually assign unique IPs, and check the DHCP server for misconfigurations.

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4
Q

What would you do if a device has an APIPA address (169.x.x.x)?

A

Check the DHCP server’s availability and ensure the device can communicate with it.

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5
Q

What tools would you use to diagnose packet loss?

A

Tools like ping, traceroute, and network analyzers (Wireshark).

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6
Q

How do you troubleshoot a routing loop?

A

Inspect routing tables, check route advertisements, and use tools like traceroute to identify loops.

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7
Q

What steps would you take for an OSPF adjacency issue?

A

Verify matching parameters (area ID, authentication), MTU settings, and ensure there are no Layer 2 issues.

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8
Q

How do you resolve BGP session flapping?

A

Check peer configurations, inspect keepalive/hold timers, and ensure stable network paths.

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9
Q

How do you troubleshoot a static route not working?

A

Verify route configuration, ensure the next-hop is reachable, and check for overlapping or conflicting routes.

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10
Q

What would you check if inter-VLAN routing is not working?

A

Verify VLAN configurations, ensure subinterfaces are configured, and check Layer 3 interfaces’ status.

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11
Q

How do you troubleshoot a VLAN mismatch?

A

Check trunk port configurations and ensure both ends have the same VLAN allowed.

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12
Q

What would you do if a specific port on a switch is not passing traffic?

A

Check the port status, verify VLAN assignment, inspect cables, and review STP status.

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13
Q

How do you troubleshoot STP-related issues?

A

Identify root bridge, check for port states, and verify priority configurations.

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14
Q

How do you resolve excessive broadcast traffic?

A

Identify the source of broadcasts using network monitoring tools and segment the network if necessary.

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15
Q

What would you check if a MAC address is not appearing in the MAC table?

A

Verify port activity, inspect VLAN settings, and ensure the device is generating traffic.

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16
Q

How do you troubleshoot a Wi-Fi network with low signal strength?

A

Check the placement of access points, adjust power levels, and scan for interference.

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17
Q

What do you do if a user cannot connect to a Wi-Fi network?

A

Verify SSID, check authentication settings, and inspect wireless logs for errors.

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18
Q

How do you resolve frequent Wi-Fi disconnections?

A

Check signal strength, review device roaming settings, and inspect AP logs.

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19
Q

What steps would you take if wireless devices experience slow speeds?

A

Analyze channel utilization, adjust channel width, and ensure no bandwidth hogging.

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20
Q

How do you identify rogue access points?

A

Use wireless scanning tools like NetSpot or AirMagnet.

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21
Q

How do you troubleshoot blocked traffic through a firewall?

A

Inspect access control lists (ACLs), check logs for denied traffic, and ensure the correct NAT configuration.

22
Q

What steps would you take if a VPN tunnel is not establishing?

A

Verify Phase 1/Phase 2 settings, check for pre-shared key mismatches, and ensure both ends are reachable.

23
Q

How do you troubleshoot port forwarding issues?

A

Ensure the correct public IP, port, and internal IP mapping. Check NAT and firewall rules.

24
Q

What do you check if a firewall is not passing traffic?

A

Verify interface statuses, review routing, and check for misconfigured security policies.

25
Q

How do you diagnose high CPU usage on a firewall?

A

Check active sessions, review traffic logs for anomalies, and ensure DDoS protection is enabled.

26
Q

What steps do you take if a website is not resolving?

A

Test with nslookup or dig, check DNS server settings, and verify the domain’s DNS records.

27
Q

How do you fix DNS timeout issues?

A

Check the DNS server’s health, ensure no network latency, and verify firewall rules.

28
Q

How do you troubleshoot intermittent DNS resolution failures?

A

Review logs, ensure redundancy, and inspect caching configurations.

29
Q

What would you check if internal DNS resolution fails?

A

Verify the DNS zone configuration, inspect replication, and check for stale records.

30
Q

How do you resolve reverse DNS lookup issues?

A

Verify PTR records and ensure they match the forward DNS records.

31
Q

How do you troubleshoot high latency in a network?

A

Use ping and traceroute to identify bottlenecks, check for congestion, and optimize QoS settings.

32
Q

What would you check if users experience frequent application timeouts?

A

Inspect the application server’s health, review network latency, and analyze logs.

33
Q

How do you troubleshoot slow file transfers over the network?

A

Test bandwidth, check for duplex mismatches, and monitor traffic for bottlenecks.

34
Q

How do you diagnose excessive CPU utilization on a router?

A

Review interface statistics, inspect routing tables, and disable unnecessary services.

35
Q

What steps would you take for network jitter issues?

A

Prioritize traffic with QoS, inspect real-time traffic paths, and reduce congestion.

36
Q

How do you detect a DDoS attack?

A

Monitor traffic patterns, check for excessive connections, and use IDS/IPS.

37
Q

What steps would you take if a network is compromised?

A

Isolate affected systems, analyze logs, and restore from backups.

38
Q

How do you secure an open port discovered during a scan?

A

Disable unused services, apply ACLs, or use a firewall.

39
Q

How do you identify unauthorized access attempts?

A

Analyze syslogs, review failed authentication attempts, and use SIEM tools.

40
Q

What would you do if sensitive data is being leaked?

A

Inspect firewall logs, review outbound traffic, and implement DLP solutions.

41
Q

How do you troubleshoot a split-horizon issue in routing?

A

Enable route redistribution and check protocol configurations.

42
Q

What do you do if multicast traffic is not being delivered?

A

Verify multicast group membership, inspect IGMP settings, and ensure PIM is configured.

43
Q

How do you resolve MTU mismatches?

A

Use ping with the -f flag and adjust MTU settings on affected devices.

44
Q

What steps would you take if QoS is not prioritizing traffic correctly?

A

Verify QoS policies, inspect traffic classification, and ensure queue settings are correct.

45
Q

How do you identify the root cause of network congestion?

A

Use tools like NetFlow, review interface statistics, and inspect traffic patterns.

46
Q

How do you troubleshoot MPLS label mismatches?

A

Verify LDP settings, check for duplicate labels, and inspect forwarding tables.

47
Q

What do you check if a VXLAN tunnel is not working?

A

Inspect VTEP settings, verify encapsulation protocols, and ensure multicast is supported.

48
Q

How do you troubleshoot SD-WAN connectivity issues?

A

Check the controller’s reachability, inspect policies, and verify transport links.

49
Q

How do you resolve issues with SNMP monitoring?

A

Verify community strings, check SNMP agent availability, and ensure firewalls allow SNMP traffic.

50
Q

What would you do if a network device firmware upgrade fails?

A

Roll back to the previous firmware, verify compatibility, and reattempt with correct procedures.

Network Engineering (2 decks)

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