Quiz — OSI Model
Test your knowledge of OSI layers, TCP/IP, and how data travels
OSI & TCP/IP — Knowledge Check
You used OSI as a location language, mapped it onto the four-layer TCP/IP stack, and walked one click through encapsulation, switches, routers, and TTL. These ten APPLY scenarios test judgment on a real path — not the sausage mnemonic. Choose the best defensive or lab move.
APPLY: A rack tech reports the server NIC has no link light. Wireshark on another host shows nothing from that server. Where do you start?
APPLY: On your home lab switch, hosts suddenly ARP the gateway but the MAC that answers is a teammate's laptop. Which layer is the incident, and what is it not?
APPLY: ping 127.0.0.1 works. ip route shows a default via. Users still cannot reach a remote subnet that your router should know. Best first OSI/TCP/IP read?
APPLY: A pcap (your VM, traffic you own) expands to Ethernet → IPv4 → TCP → HTTP. A teammate says OSI is false because there is no Session header. Your correction?
APPLY: You need to show a junior the difference between L2 and L3 on a machine you own. Which commands match that job?
APPLY: True or False: On the first hop, the Ethernet destination is usually the default gateway's MAC, even when the IP destination is a remote server.
APPLY: Firewall policy allows tcp/443 from 10.0.1.0/24 to 10.0.2.50. Which TCP/IP layers is that rule actually matching?
APPLY: A classmate runs traceroute against a hospital network "to learn TTL" from the coffee-shop Wi-Fi. Best assessment?
APPLY: Users report a convincing fake login page served over HTTPS. DNS resolves. TCP connects. Which daily SOC layer is the content of the attack, and what did the lower layers still do?
APPLY: True or False: traceroute prints hops because each router decrements TTL; a probe that hits zero should elicit Time Exceeded — so * * * can mean the hop filtered ICMP, not that every protocol is dead.