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Computer networking under the hood

The author created this network study guide by breaking down large subject into small topics, so that we can learn each topic in detail. Computer networking is the foundation of modern society. Here we discuss computer networks built on hardwares, cloud computing, though based on the concepts studied here, is not discussed in this course.

Do It Yourself (DIY) is the best way of learning TCP/IP network, therefore, I highly recommend you to download wireshark and packet tracer. With wireshark, you can capture your network traffic and see exactly what's going on under the hood; with packet tracer, you can set up LAN and WAN virtually and do experiments on them. With some spare bucks, you can even setup a WAN lab at home by purchasing some cisco equipments.

Knowing networking technology is not only fun, it can also get you hired. The most popular network certification is Cisco CCENT and CCNA. If you haven't decided what CCNA test to take, read this post first. Also check out the Cisco device based networking Lab for the labs corresponding to this tutorial.

Whenever you need to learn more about a networking key word, use the Site Search at the upper left conner.

Good luck with your study and test!


Lesson 1
Networking Fundamentals and the Networking Models

In this first lesson, we talk about what is network in general. OSI model and TCP/IP model are visited. These models break network communication into smaller, simpler layers, which make learning easier. Within the context of network layers, the data transmission process is discussed, you will get a bird-view of how the internet makes your web surfing works even at the bit (electromagnetic pulse in cable wires) level. Several famous protocols are introduced: TCP, UDP, IP and ICMP. You will understand the concepts of Ports, Sockets and Port numbers, which are important to software engineers as well as network administrators. Finally, a few common TCP/IP network applications -- FTP, telnet, http are examined with wireshark, so that you get an sense of how these everyday magic happens under the hood.

What is A Network
The TCP/IP Model
The OSI Model
The Data Transmission Process
IP and ICMP protocols
Ports, Sockets and Port Numbers
TCP/IP Applications
Network Topology

Lesson 2
Ethernet Standards and Cable Types

In this foot on the ground lesson, we delve into Ethernet standards and cable types. You will know about connectors such as RJ-11, RJ-45, fiber-optic GBIC and cable types such as UTP, STP, Fiber Optic. You will understand the category of UTP cables, so that when your cable guy says "Your home needs at least Cat 5", you can remain cool. You even gain knowledge about the pins on a cable, able to differentiate a straight-through cable from a crossover cable. Once two computers are connected with a cable, they need to communicate via the electromagnetic pulses in the cable wires. Physicists in the last century took a lot of effort to figured it out. This know how is the foundation of internet. We will learn this know how in topics CSMA/CD, Ethernet frame, ethernet addressing and host-to-host communication. This lesson has a lot of nitty-ditty details, but is crucial for setting up and trouble-shooting a real-world network made of metal and plastics.

What is a LAN
Ethernet Types And Standards
The Need For And Operation of CSMA/CD
Ethernet Frame
Ethernet Addressing
Host-to-Host Communication
Ethernet Connectors and Cable Types
Pins And Transmissions

Lession 3

Now we know how 2 computers talk to each other, this lesson will study how a group of computers talk to each other. To make this happen, switching is a must. In this lesson we will met layer 1 devices repeaters and hubs, layer 2 devices bridges and switches, layer 3 device routers. While hubs and repeaters allow group computers to share links, switches and bridges divide computer groups in LANs. Routers defines the boundary of LANs.

Ethernet LAN Segments
Repeaters, Hubs, Bridges, Switches and Routers
MAC address learning and filter/forward decisions
Frame Processing Methods
Virtual LANs
Cisco Three-Layer Switching Model
Introduction to STP
Basic Switch Security

Lesson 4
Common Router and Switch Commands

Typical Switch (And Router) Commands are studied here, these commands are used daily by network administrators.

Video Lab - Packet Tracer Interface Overview
Physical Connections and Passwords
Cisco IOS software overview
Physical Side of Cisco Switches
User, Enable and Privilege Modes
Basic Switch managment commands
Switch/Router passwords configurations
Telnet and SSH
Switch Port Security Defaults, Options and Configurations
Banners“logging synch”, and “exec-timeout”
Keystroke Shortcuts and Manipulating History

Lesson 5
IP Addressing and the Routing Process

This lesson covers the fundamental concepts for IP addressing: binary math, subnetting, and working with network and port address translations.

IP Addressing and Binary Conversions
IP Address Classes
Private IP Address Ranges
CIDR network address
Intro to the Routing Process
Routing Process Continued -- Behind the "PING"
* Routing Protocols
Basic Router management commands
Switch/Router Interfaces and Physical Ports

Lesson 6

DNS Process
The ARP RARP and DHCP Process
Broadcast, Multicast, and Unicast
Intro to Security Device Manager (SDM)

Lesson 7
Memory Components and Config Files

This lesson covers basic password and security configurations, as well as assigning privilege levels, which is the foundation of router security and the basic password recovery process.

ROM, RAM, NVRAM, And Flash
The Boot Process
Setup Mode
Configuration Files and IOS Upgrading
The Configuration Register

Lesson 8
Intro to Wireless Networks (WLANs)

Learn the protocol as well as physics side of wireless.

Wireless LAN overview
Wireless Standards
Spread Spectrum
Antena Types
CA vs. CD
SSID, MAC Address Authentication, WEP, WPA, and WPA2

Lesson 9
Binary Math and Subnetting

The content learned in this lesson is essential for IP addressing and IP address conservation.

Decimal > Binary, Binary > Decimal
Subnetting Basics
Four common subnetting scenarios

Lesson 10
Static Routing and RIP – Part 1

In this lesson, you will see the work done over a Cisco router. You will learn how to manually set up routing.

Static Routing Theory
Floating Static Routing
RIP Routing Theory
Video Lab -Static Routing and RIP Routing

Lesson 11
Wide Area Networks (WANs)

LAN and WAN are build on OSI layer 1 and layer 2, where cable details such as transmission speeds, encoding, frames and physical links etc. are defined. We have learned LAN before, here lets talk about WAN. Compared with LAN, LAN usually covers a small distance, while WAN spans across a large geographic area. Your party owns LAN, but you most likely share WAN with other parties, so you probably don't have rights to modify the WAN infrastructure.

What is a WAN
Physical Side of WANs
WAN interface of Cisco Router and WAN Cabling
* Layer 2 WAN encapsulations
Intro to Frame Relay
* NAT overloading Example
Video Lab - Internet Connections with NAT and PAT
Video Lab - Router as DHCP Server
Intro to ATM
Modems and DSL Variations
WAN Trouble-shooting

Lesson 12

Introduction to Network Security

Network security has become more and more important in today's internet. In this lesson, you will learn about network attackers and intruders, how they get in, and how to keep your network save by keeping them out.

The need for network security
Classes of Hacker Attacks
Firewalls and Proxy Servers
The Attacker’s Arsenal
Intro to PIX, ASA, IDS, and IPS
Viruses, Worms, and Trojan Horses
Preventing Virus Attacks

Lesson 13

95% of work in the real world is troubleshooting, so it’s necessary for real world success.

Cisco Discovery protocol (CDP)
L1 and L2 Troubleshooting
Telnet and SSH Maintenance Commands
* Administrative Distance
Extended Ping and Traceroute


Lesson 1
Switching II

This lesson revisits the basic concepts of switch and VLAN learned in CCENT, adds more cisco labs about how to configure the switch and router for VLAN.

Switch Basic Concept Review
* Root Bridges, Root Ports, and Designated Ports
* STP Timers and Port States
* Portfast
* VLANs and Trunking
* Access and Trunk Port Comparison
* “Router on a Stick”
* Etherchannels

Lesson 2
PTP WAN Links, HDLC, PPP, and Frame Relay

This lesson is about Frame Relay.

* HDLC vs. PPP
* WAN Topology
* PPP Features
* PAP and CHAP
* Frame Relay Introduction
* Frame Relay LMI Theory
* Frame Relay Configs, DLCIs, Frame Maps, and Inverse ARP
* Frame Sub-Interfaces3
* Split Horizon
* Frame Relay LMI Show, Debug, and Lab
* FECN, BECN, DE bits
* PVC Status Meanings

Lesson 3
Static Routing and RIP

covering advanced topics about RIP.

* Static Routing Theory and Configuration
* Distance Vector Protocol Behavior – Split Horizon and Route Poisoning
* RIP Theory and Version Differences
* The Joy of “show ip protocols”
* RIP Limitations
* RIP Timers
* Floating Static Routes

Lesson 4

OSPF is an Internet protocol we need to know how to configure.

* Link State Routing Protocol Concepts and Basics
* The DR and BDR
* Hello Packets
* Troubleshooting Adjacency Issues
* Hub-and-Spoke NBMA OSPF Networks
* Broadcast Networks
* OSPF Router Types
* Advantages of OSPF
* Point-to-Point OSPF Networks
* Default-Information Originate (always?)
* OSPF Authentication

Lesson 5

this hybrid routing protocol has increased operational efficiency from it predecessor.

* Introduction to EIGRP
* Successors and Feasible Successors
* EIGRP vs. RIPv2
* Basic Configuration
* Wildcard Masks
* Load Sharing (Equal and Unequal-cost)
* EIGRP, RIPv2, and Autosummarization
* Passive vs. Active Routes

Lesson 6
IP Version 6 and NAT

Learn the basic theory and routing protocol of IP version 6.

* IPv6 Theory and Introduction
* Zero Compression and Leading Zero Compression
* IPv6 Reserved Addresses
* The Autoconfiguration Process
* OSPF v3 Basics
* Transition Strategies
* NAT Theory and Introduction
* Static NAT Configuration
* Dynamic NAT Configuration
* PAT Configuration

Lesson 7
VPNs and IPSec

This lesson is about how to setup and run a VPN network.

* Definitions and Tunneling Protocols
* Data Encryption Technologies
* Key Encryption Schemes
* IPSec, AH and ESP
* A VPN in Your Web Browser

Lesson 8
ACLs and Route Summarization

Learn to configure and control ACLs. Learn the basic breakdown and how to summarize routes. Learn common commands for working with RIP & EIGRP.

* ACL Login and the Implicit Deny
* Standard ACLs and Remarks
* “Host” and “Any”
* The Order of the Lines
* Extended ACLs
* Named ACLs
* Telnet Access, Placing ACLs, and Blocking Pings
* Dynamic and Time-Based ACLs
* Port Number Review
* Route Summarization with RIP and EIGRP

See also 640-822 ICND1 Exam Topics (Blueprint)