Show:
OSI Layers
TCP/IP Model
Protocols & Ports
Encapsulation & Addresses
Troubleshooting
100

Which OSI layer turns bits into signals?

Physical

100

TCP/IP layer for HTTP/DNS?

Application

100

Translates names to IPs?

DNS

100

Layer 2 PDU?

Frame

100

No link light → check what layer first?

Physical

200

Builds frames + uses MAC?

Data Link

200

TCP/IP layer for TCP/UDP?

Transport

200

Maps IPv4 to MAC?

ARP

200

Layer 3 PDU?

Packet

200

Name fails, IP works → likely issue?

DNS

300

Logical addressing/routing (IP)?

Network

300

TCP/IP layer with IP routing?

Internet

300

HTTPS port?

443

300

Layer 4 (TCP) PDU?

Segment

300

Ping works, HTTPS fails → likely cause?

TCP 443 blocked

400

Uses ports + reliability?

Transport

400

TCP/IP layer for Ethernet/Wi‑Fi?

Network Access

400

DHCP ports (server/client)?

67/68

400

Off-subnet: first frame dest MAC?

Default gateway

400

High CRC errors usually indicate?

Physical/cabling/duplex

500

Encryption/compression layer?

Presentation

500

OSI layers inside TCP/IP Application layer?

OSI 5–7

500

Ping relies on:
A) TCP
B) UDP
C) ICMP?

ICMP

500

What changes each hop (no NAT): IP or MAC?

MAC

500

Large transfers fail unless MTU lowered → why?

Path MTU/PMTUD issue