Linux · Networking interview questions

75 real Linux · Networking questions from the System Administration bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What does ss -tulpn do?

Junior
  1. A.list listening TCP/UDP ports with their owning process PIDs
  2. B.capture and inspect network packets on an interface
  3. C.show or change NIC settings like speed and duplex
  4. D.show the network hops to a destination
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3. Which statement is correct?

Junior
  1. A.ss -tulpn — show interface statistics including dropped packets
  2. B.ss -tulpn — fetch only the HTTP response headers from a URL
  3. C.ss -tulpn — persistently open HTTPS in firewalld (apply after --reload)
  4. D.ss -tulpn — list listening TCP/UDP ports with their owning process PIDs
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4. What does ip addr do?

Junior
  1. A.show the network hops to a destination
  2. B.capture and inspect network packets on an interface
  3. C.show network interfaces and their IP addresses
  4. D.apply firewalld's permanent config without dropping connections
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6. Which statement is correct?

Junior
  1. A.ip addr — show network interfaces and their IP addresses
  2. B.ip addr — list NetworkManager connection profiles
  3. C.ip addr — send 4 ICMP echo requests to test reachability
  4. D.ip addr — resolve a hostname to its IP using DNS
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7. What does ip route do?

Junior
  1. A.show the active rules of the default firewalld zone
  2. B.show the kernel routing table
  3. C.activate a NetworkManager connection profile
  4. D.show or change NIC settings like speed and duplex
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9. Which statement is correct?

Junior
  1. A.ip route — fetch only the HTTP response headers from a URL
  2. B.ip route — show the kernel routing table
  3. C.ip route — activate a NetworkManager connection profile
  4. D.ip route — show interface statistics including dropped packets
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12. Which statement is correct?

Junior
  1. A.ip link set eth0 up — bring the network interface eth0 up
  2. B.ip link set eth0 up — capture and inspect network packets on an interface
  3. C.ip link set eth0 up — list listening TCP/UDP ports with their owning process PIDs
  4. D.ip link set eth0 up — show or change NIC settings like speed and duplex
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15. Which statement is correct?

Mid
  1. A.nmcli con show — capture and inspect network packets on an interface
  2. B.nmcli con show — apply firewalld's permanent config without dropping connections
  3. C.nmcli con show — list NetworkManager connection profiles
  4. D.nmcli con show — persistently open HTTPS in firewalld (apply after --reload)
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16. What does firewall-cmd --permanent --add-service=https do?

Mid
  1. A.persistently open HTTPS in firewalld (apply after --reload)
  2. B.show network interfaces and their IP addresses
  3. C.list NetworkManager connection profiles
  4. D.show interface statistics including dropped packets
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18. Which statement is correct?

Mid
  1. A.firewall-cmd --permanent --add-service=https — resolve a hostname to its IP using DNS
  2. B.firewall-cmd --permanent --add-service=https — persistently open HTTPS in firewalld (apply after --reload)
  3. C.firewall-cmd --permanent --add-service=https — list NetworkManager connection profiles
  4. D.firewall-cmd --permanent --add-service=https — activate a NetworkManager connection profile
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19. What does firewall-cmd --reload do?

Mid
  1. A.query DNS records from the command line
  2. B.apply firewalld's permanent config without dropping connections
  3. C.show the network hops to a destination
  4. D.show network interfaces and their IP addresses
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21. Which statement is correct?

Mid
  1. A.firewall-cmd --reload — send 4 ICMP echo requests to test reachability
  2. B.firewall-cmd --reload — apply firewalld's permanent config without dropping connections
  3. C.firewall-cmd --reload — list listening TCP/UDP ports with their owning process PIDs
  4. D.firewall-cmd --reload — resolve a hostname to its IP using DNS
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22. What does dig do?

Junior
  1. A.persistently open HTTPS in firewalld (apply after --reload)
  2. B.show the kernel routing table
  3. C.query DNS records from the command line
  4. D.show the active rules of the default firewalld zone
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24. Which statement is correct?

Junior
  1. A.dig — show network interfaces and their IP addresses
  2. B.dig — persistently open HTTPS in firewalld (apply after --reload)
  3. C.dig — show the kernel routing table
  4. D.dig — query DNS records from the command line
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25. What does tcpdump do?

Mid
  1. A.show or change NIC settings like speed and duplex
  2. B.capture and inspect network packets on an interface
  3. C.resolve a hostname to its IP using DNS
  4. D.persistently open HTTPS in firewalld (apply after --reload)
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27. Which statement is correct?

Mid
  1. A.tcpdump — show interface statistics including dropped packets
  2. B.tcpdump — show the active rules of the default firewalld zone
  3. C.tcpdump — show network interfaces and their IP addresses
  4. D.tcpdump — capture and inspect network packets on an interface
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28. What is /etc/resolv.conf?

Junior
  1. A.a kernel check (rp_filter) that drops packets arriving on the wrong interface
  2. B.the file listing the DNS nameservers the system uses
  3. C.dropped connections when the netfilter connection-tracking table fills
  4. D.serving different DNS answers to internal vs external clients
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30. Which statement is correct?

Junior
  1. A./etc/resolv.conf — the file mapping static hostnames to IP addresses, checked before DNS
  2. B./etc/resolv.conf — 802.3ad LACP link aggregation for bandwidth and failover
  3. C./etc/resolv.conf — dropped connections when the netfilter connection-tracking table fills
  4. D./etc/resolv.conf — the file listing the DNS nameservers the system uses
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