Operating Systems and Networking
Operating Systems and Networking tests how processes, files, users and packets are managed, plus basic IPv4 design and troubleshooting.
Core rules
- An OS schedules processes, allocates memory, manages files and permissions, and exposes devices through drivers.
- TCP/IP layering: application, transport, internet and link. TCP is connection-oriented and reliable; UDP is connectionless.
- Private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. NAT lets private hosts share a public address.
- DNS resolves names; DHCP leases addresses; the default gateway routes off-subnet traffic.
Worked example
For 192.168.10.64/26, the mask has 26 bits, leaving 6 host bits. Block size is 2^6 = 64 addresses. The network is .64, broadcast is .127, and usable hosts are .65 to .126, giving 62 hosts. A host at .130 is therefore not in this subnet; it belongs to .128/26. Check the host against the network and broadcast boundaries before blaming the cable.
Traps
Do not call a private address routable on the internet; do not confuse DNS with DHCP; do not omit the network and broadcast addresses when counting usable hosts; and do not troubleshoot a name-resolution failure as a link failure before testing ping to an IP address.