CCNA Networking · Quick Reference

Module 3 — Protocols and Models Cheat Sheet

CCNA Networking

In one line: All communication — whether human language or network data — requires three things: a source (the sender), a channel (the medium that carries the message), and a destination (th...

Key Ideas

1Communication Fundamentals. All communication — whether human language or network data — requires three things: a source (the sender), a channel (the medium that carries the message), and a desti...

2Delivery Options 📩 Unicast One-to-one communication. The most common delivery method. A single source sends to a single specific destination. Most Common 📢 Multicast One-to-many specific group. Data is sent to a group of interested receivers. Used for streaming, routing protocols (OSPF, EIGRP). Group Delivery 📡 Broadcast One-to-all on the network segment. Every device receives the message. Used by ARP, DHCP. Limited to the local network. All Devices Section 2 Network Protocols. A protocol is a set of rules that defines exactly how communication happens between devices. Without protocols, devices from different manufacturers could never commun...

3TCP/IP Protocol Suite. The TCP/IP protocol suite is the actual standard used by the internet and all modern networks. It is defined in open RFC (Request for Comments) documents. TCP/IP has f...

4The OSI Reference Model. The OSI model (Open Systems Interconnection) was developed by the ISO to provide a universal reference framework for how different network systems could communicate re...

5OSI vs TCP/IP Comparison. Both models describe the same network communication, but from different perspectives. TCP/IP is the practical implementation; OSI is the theoretical reference. They ma...

Code Examples

! Web browser visiting https://bitwithbite.com
!
! Layer 7 - Application: HTTP/HTTPS request
GET /index.html HTTP/1.1
Host: bitwithbite.com
!
! Layer 4 - Transport: TCP segment
! Source Port: 49152 (random ephemeral)
! Destination Port: 443 (HTTPS)
...