Computer Networks and Internet
What this domain tests
Computer Networks and Internet tests topologies, layers, addressing, devices, protocols and services. Questions mix definitions with small IP calculations.
Core rules
- Topologies: bus, star, ring, mesh, tree, hybrid. Star is common in LANs; mesh gives redundancy at higher cost.
- TCP/IP layers: application, transport, internet, network access. OSI has seven layers: physical, data link, network, transport, session, presentation, application.
- Devices: hub repeats to all ports; switch forwards by MAC address; router forwards by IP address; modem modulates/demodulates.
- IPv4 is 32-bit; IPv6 is 128-bit. Private ranges include 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
- DNS resolves names to IP addresses; DHCP assigns addresses; HTTP/HTTPS transfer web pages; SMTP sends mail, POP3/IMAP retrieves it.
Worked example
For 192.168.1.10/24: mask = 255.255.255.0. Network address = 192.168.1.0; broadcast = 192.168.1.255; usable host range = 192.168.1.1–192.168.1.254, so 254 hosts. Reasoning: /24 leaves 8 host bits; 2^8 = 256 addresses, minus network and broadcast.
Traps
Do not say a hub filters by MAC address. HTTPS is HTTP over TLS, not a different application protocol. DNS does not assign IP addresses; DHCP does. A /24 does not provide 256 usable hosts. Do not confuse the network address with the first usable host.