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LPIC-1 102-500 study materials
LPIC-1 102-500 study resources

LPIC-1 102-500: Networking Fundamentals

LPIC-1 102-500 · Work through your exam, one topic at a time.

All guide sections

Networking Fundamentals

What the exam tests

Networking Fundamentals covers IP addressing, persistent configuration, troubleshooting, and client-side DNS. Expect command output interpretation and configuration-file locations.

Core rules

  • IPv4 private ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16; loopback is 127.0.0.0/8; link-local is 169.254.0.0/16. IPv6 loopback is ::1, link-local is fe80::/10, global unicast is 2000::/3, and multicast is ff00::/8. CIDR /24 gives 256 addresses, 254 usable.
  • Ports and protocols: TCP 22 SSH, 25 SMTP, 53 DNS, 80 HTTP, 123 NTP, and 443 HTTPS; /etc/services maps names to ports. ICMP supports ping; UDP is connectionless.
  • Persistent config: NetworkManager uses nmcli con mod and stores profiles in /etc/NetworkManager/system-connections/; nmtui is the text UI. systemd-networkd uses .network files. Debian ifupdown uses /etc/network/interfaces.
  • Troubleshooting: ip addr, ip route, ss -tulpn, ping, traceroute, dig, host, getent hosts, and resolvectl. Check link, address, route, then name resolution.
  • DNS client: /etc/resolv.conf lists nameserver and search; /etc/hosts provides static entries; /etc/nsswitch.conf controls order, commonly hosts: files dns.

Worked example

A host can ping 192.0.2.10 but not db.lab. ip route shows a default route, and ping 192.0.2.10 succeeds, so L3 connectivity is fine. cat /etc/resolv.conf shows no nameserver. Add nameserver 192.0.2.53, then test with getent hosts db.lab and dig db.lab. Reasoning: getent uses NSS and reflects application behavior; dig queries DNS directly. If getent fails while dig succeeds, inspect /etc/nsswitch.conf and /etc/hosts.

Traps

Editing /etc/resolv.conf directly may be overwritten by NetworkManager or resolvconf; change the connection profile. ping uses ICMP and may be blocked while TCP works. A route to a host does not guarantee DNS. ss -l shows listening sockets; ss -t shows TCP sockets. Do not confuse the default gateway with a DNS server. IPv6 link-local addresses need a zone ID such as %eth0.