Interview Questions Flashcards
What steps would you take if a user reports no internet connectivity?
Check the physical connection, verify IP settings, test connectivity with ping, check for DHCP issues, and ensure the gateway is reachable.
How do you troubleshoot a failed ping test to a specific server?
Verify server availability, check DNS resolution, ensure correct routing, and inspect firewalls for blocked ICMP.
How do you resolve duplicate IP address conflicts?
Identify conflicting devices using arp -a, manually assign unique IPs, and check the DHCP server for misconfigurations.
What would you do if a device has an APIPA address (169.x.x.x)?
Check the DHCP server’s availability and ensure the device can communicate with it.
What tools would you use to diagnose packet loss?
Tools like ping, traceroute, and network analyzers (Wireshark).
How do you troubleshoot a routing loop?
Inspect routing tables, check route advertisements, and use tools like traceroute to identify loops.
What steps would you take for an OSPF adjacency issue?
Verify matching parameters (area ID, authentication), MTU settings, and ensure there are no Layer 2 issues.
How do you resolve BGP session flapping?
Check peer configurations, inspect keepalive/hold timers, and ensure stable network paths.
How do you troubleshoot a static route not working?
Verify route configuration, ensure the next-hop is reachable, and check for overlapping or conflicting routes.
What would you check if inter-VLAN routing is not working?
Verify VLAN configurations, ensure subinterfaces are configured, and check Layer 3 interfaces’ status.
How do you troubleshoot a VLAN mismatch?
Check trunk port configurations and ensure both ends have the same VLAN allowed.
What would you do if a specific port on a switch is not passing traffic?
Check the port status, verify VLAN assignment, inspect cables, and review STP status.
How do you troubleshoot STP-related issues?
Identify root bridge, check for port states, and verify priority configurations.
How do you resolve excessive broadcast traffic?
Identify the source of broadcasts using network monitoring tools and segment the network if necessary.
What would you check if a MAC address is not appearing in the MAC table?
Verify port activity, inspect VLAN settings, and ensure the device is generating traffic.
How do you troubleshoot a Wi-Fi network with low signal strength?
Check the placement of access points, adjust power levels, and scan for interference.
What do you do if a user cannot connect to a Wi-Fi network?
Verify SSID, check authentication settings, and inspect wireless logs for errors.
How do you resolve frequent Wi-Fi disconnections?
Check signal strength, review device roaming settings, and inspect AP logs.
What steps would you take if wireless devices experience slow speeds?
Analyze channel utilization, adjust channel width, and ensure no bandwidth hogging.
How do you identify rogue access points?
Use wireless scanning tools like NetSpot or AirMagnet.
How do you troubleshoot blocked traffic through a firewall?
Inspect access control lists (ACLs), check logs for denied traffic, and ensure the correct NAT configuration.
What steps would you take if a VPN tunnel is not establishing?
Verify Phase 1/Phase 2 settings, check for pre-shared key mismatches, and ensure both ends are reachable.
How do you troubleshoot port forwarding issues?
Ensure the correct public IP, port, and internal IP mapping. Check NAT and firewall rules.
What do you check if a firewall is not passing traffic?
Verify interface statuses, review routing, and check for misconfigured security policies.
How do you diagnose high CPU usage on a firewall?
Check active sessions, review traffic logs for anomalies, and ensure DDoS protection is enabled.
What steps do you take if a website is not resolving?
Test with nslookup or dig, check DNS server settings, and verify the domain’s DNS records.
How do you fix DNS timeout issues?
Check the DNS server’s health, ensure no network latency, and verify firewall rules.
How do you troubleshoot intermittent DNS resolution failures?
Review logs, ensure redundancy, and inspect caching configurations.
What would you check if internal DNS resolution fails?
Verify the DNS zone configuration, inspect replication, and check for stale records.
How do you resolve reverse DNS lookup issues?
Verify PTR records and ensure they match the forward DNS records.
How do you troubleshoot high latency in a network?
Use ping and traceroute to identify bottlenecks, check for congestion, and optimize QoS settings.
What would you check if users experience frequent application timeouts?
Inspect the application server’s health, review network latency, and analyze logs.
How do you troubleshoot slow file transfers over the network?
Test bandwidth, check for duplex mismatches, and monitor traffic for bottlenecks.
How do you diagnose excessive CPU utilization on a router?
Review interface statistics, inspect routing tables, and disable unnecessary services.
What steps would you take for network jitter issues?
Prioritize traffic with QoS, inspect real-time traffic paths, and reduce congestion.
How do you detect a DDoS attack?
Monitor traffic patterns, check for excessive connections, and use IDS/IPS.
What steps would you take if a network is compromised?
Isolate affected systems, analyze logs, and restore from backups.
How do you secure an open port discovered during a scan?
Disable unused services, apply ACLs, or use a firewall.
How do you identify unauthorized access attempts?
Analyze syslogs, review failed authentication attempts, and use SIEM tools.
What would you do if sensitive data is being leaked?
Inspect firewall logs, review outbound traffic, and implement DLP solutions.
How do you troubleshoot a split-horizon issue in routing?
Enable route redistribution and check protocol configurations.
What do you do if multicast traffic is not being delivered?
Verify multicast group membership, inspect IGMP settings, and ensure PIM is configured.
How do you resolve MTU mismatches?
Use ping with the -f flag and adjust MTU settings on affected devices.
What steps would you take if QoS is not prioritizing traffic correctly?
Verify QoS policies, inspect traffic classification, and ensure queue settings are correct.
How do you identify the root cause of network congestion?
Use tools like NetFlow, review interface statistics, and inspect traffic patterns.
How do you troubleshoot MPLS label mismatches?
Verify LDP settings, check for duplicate labels, and inspect forwarding tables.
What do you check if a VXLAN tunnel is not working?
Inspect VTEP settings, verify encapsulation protocols, and ensure multicast is supported.
How do you troubleshoot SD-WAN connectivity issues?
Check the controller’s reachability, inspect policies, and verify transport links.
How do you resolve issues with SNMP monitoring?
Verify community strings, check SNMP agent availability, and ensure firewalls allow SNMP traffic.
What would you do if a network device firmware upgrade fails?
Roll back to the previous firmware, verify compatibility, and reattempt with correct procedures.
