mrsh/CCNA-Notes
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

update to 05.Ethernet Lan Switching

Browse Source
This commit is contained in:
mrsh
2026-04-23 15:39:02 +02:00
parent 864a6c874f
commit 0353df0ed2
7 changed files with 744 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
00. Jeremy's IT LAB CCNA course.md Normal file
View File

@@ -0,0 +1,17 @@
---
id: Jeremy's IT LAB CCNA course
aliases: []
tags:
- CCNA
---
# Jeremy's IT LAB CCNA course
[link](https://www.youtube.com/watch?v=H8W9oMNSuwo&list=PLxbwE86jKRgMpuZuLBivzlM8s2Dk5lXBQ)
[drive](https://drive.google.com/drive/folders/1PwK_jWqfUtOjV7gHt8ODutq9QA5cxCgi)
[[Network Devices - CCNA]]
[[Interfaces and Cables - CCNA]]
[[How the TCPIP Model Actually Works]]
[[Intro to the CLI]]
[[Ethernet LAN Switching]]

132
01. Network Devices - CCNA.md Normal file
View File

@@ -0,0 +1,132 @@
---
id: 1771668476-SUCR
aliases:
- 01. Network Devices - CCNA
tags:
- CCNA
---
# Network Devices
## What is a network
A computer network is a digital telecommunications network which allows nodes to share resources.
### [[Router]]
Is represented with a circle where inside there are 2 horizontal arrow poiting
inside and 2 vertical arrow pointing outside
Have fewer network interfaces than switches
Are used to provide connectivity **between** LANs
Are therefore used to send data over the Internet
example of [[Cisco]] routers:
- [[ISR 1000]]
- [[ISR 900]]
- [[ISR 4000]]
### [[Switch]]
Is represented with square 4 horizontal 2 poiting to the left and 2 pointing to the right
Switches a used to connect a [[LAN]]
Have many network interfaces/oirts for end hosts to connect to (usually 24)
Provide connectivity to hosts within the same LAN
do not provide connectivity between LANs/ over the internet
example of [[Cisco]] switches:
- [[Catalyst 9200]]
- [[Catalyst 3650]]
### [[Firewall]]
Is represented with square with a brickwall inside of it
Monintor and control network traffic based on configured rules.
Can be placed 'Inside' the network, or 'outside' the network
Are known as 'Next-Generation Firewall' when they include more modern and advanced filtering capabilities
example of [[Cisco]] firewalls:
- [[ASA 5500-X]]
- [[Firepower 2100]]
#### Host-based firewalls
Are software applications that filter traffic entering and exiting a host machine, like a [[PC]]
### [[Server]]
Is represented with square with a computer inside of it
**A device that provides functions or services for clients.**
The same device can be a client in some situations, and a server in other situations.
### [[Client]]
Is represented with square with a monitor inside of it
Can be a computer, a laptop, or a phone
**A client is a device that accesses a service made available by a server.**
### [[Internet]]
Is represented with circle with a cloud inside of it
## Building a network
2 pc connected together create a network
## Quiz
1. Your company wants to purchase some network hardware to which they can plug the 30 PCs in your department.
which type of network device is appropriate?
a) A router
b) A firewall
c) A switch
d) A server
**good answer: c**
2. You received a video file from your friend's [[Apple]] [[iPhone]] using [[AirDrop]].
What was his iPhone functioning as in that transaction?
a) A server
b) A client
c) A LAN
**good answer: a**
3. what is your computer or smartphone functioning as while you watch this video?
a) A server
b) An end host
c) A client
**good answer: c**
4. Your company wants to purchase some network hardware to connect its separate network together.
what kind of network device is appropriate ?
a) A firewall
b) A host
c) a LAN
d) A router
**good answer: d**
5. Your company wants to upgrade its old network firewall that has been in use for several years to one that provides more advanced function.
What kind of firewall should they purchase ?
a) A host-based firewall
b) A next-level firewall
c) A next-generation firewall
d) A top-layer firewall
**good answer: c**

184
02. Interfaces and Cables - CCNA.md Normal file
View File

@@ -0,0 +1,184 @@
---
id: 1771825730-VZFA
aliases:
- 02. Interfaces and Cables - CCNA
tags:
- CCNA
---
# Interfaces and Cables
Front of a switch example phrase above the interfaces
10/100/1000 Base-T Ports ( 1 -24) - Ports are Auto MDIX
## [[RJ-45]]
Registerred Jack
## Etrhernet
Etrhernet is a collection of network protocols/standards.
## Network Protocols
Why do we need network protocols
For Industry standard that everybody follows
## [[Bits]] and [[Bytes]]
it a value represented by 0 and 1
a bytes is a series of 8 bits
Speed is measured in bits per second (kbps, Mbps, Gbps, etc) not bytes per seconds.
However for [[Hard drives]] we count the bytes
1 kilobit (kb) - 1,000 bits
1 megabit (Mb) - 1,000,000 bits
1 gigabit (Gb) - 1,000,000,000 bits
1 terabit (Tb) - 1,000,000 bits
## Etrhernet standards
- Defined in the IEEE 802.3 standard in 1983
- IEEE = Institute of Electrical and Electronics Engineers
### Copper Ethernet standard
| Speed | Common name | IEEE | Informal Name | Maximum Length |
| ------- | ------------------- | --------- | ------------- | -------------- |
| 10 Mbps | Ethernet | 802.3i | 10BASE-T | 100m |
| 100 Mbps| Fast Ethernet | 802.3u | 100BASE-T | 100m |
| 1 Gbps | Gigabit Ethernet | 802.3ab | 1000BASE-T | 100m |
| 10 Gbps | 10 Gig Ethernet | 802.3an | 10GBASE-T | 100m |
#### BASE T
Base = refers to baseband signaling
T = twitsted pair
### UTP Cables
Unshielded Twisted Pair
Twisted mean that there sensitive against [[EMI]] Electronic Magnetic Interference
they got 8 pins
10Base-T and 100Base-T = 2 pairs (4 wires)
1000Base-T and 10GBase-T = 4pairs (8 wires)
#### UTP Cables (10Base-T, 100 Base-T)
Full-Duplex transmission
Both devices can send and received data at the same. no colission while occur
##### Straight-through cable
Transmit 1 - 1 Receive
(TX) 2 - 2 (RX)
Recieve 3 - 3 Transmit
4 4
5 5
(RX) 6 - 6 (TX)
7 7
8 8
##### Crossover cable
Transmit 1 - 3 Transmit
(TX) 2 - 6 (TX)
Recieve 3 - 1 Receive
4 4
5 5
(RX) 6 - 2 (RX)
7 7
8 8
##### Chart
| Device Type | Transmit (TX) Pins | Recieve (RX) Pins |
| ----------- | ------------------ | ----------------- |
| [[Router]] | 1 and 2 | 3 and 6 |
|[[Firewall]] | 1 and 2 | 3 and 6 |
| [[PC]] | 1 and 2 | 3 and 6 |
| [[Switch]] | 3 and 6 | 1 and 2 |
##### Auto MDI-X
allows devices to automatically detect and adjust the the pins for transmiting data prevent colissions
#### UTP Cables (10Base-T, 100 Base-T)
##### Straight-through cable
Each pair is bidirectional
the pair are
1 and 2
3 and 6
4 and 5
7 and 8
## Fiber-Optic Connection
[[SFP]] Transceiver Small-Factor Pluggable for Fiber Optics cable
Send light over glass fiber
TX - RX
RX - TX
there are 4 layers for this cable
1 : the fiberglass core itself
2 : cladding that reflects light
3 : a protective buffer
4 : the outer jacket of the cable
single-mode and multimode fiber
### Multimode fiber
- Core diameter is wider than single mode fiber.
- Allow mutiple angles (modes) of light waves to enter the fiberglass core
- Allows longer cables tha [[UTP]] but shorter cables than single-mode fiber.
- cheaper than single-mode fiber (due to cheaper LED-based SFP transmitters)
### Single-Mode Fiber
- Core diameter is narrower than multimode fiber
- Light enters at a single angle (mode) from alaser-based transmitter
- Allows longer cables than both UTP and multimode fiber
- More expensive than multimode fiber (due to more expnesive laser based transmitters)
### Fiber-Optic cables standards
| Speed | Cable Type | IEEE | Informal Name | Maximum Length |
| ------- | ------------------- | --------- | ------------- | ---------------- |
| 1 Gbps | multi or single-mode| 802.3z | 1000BASE-LX | 550m(MM) 5km (SM)|
| 10 Gbps | Multi-mode | 802.3ae | 10GBASE-SR | 400m |
| 10 Gbps | Single-Mode | 802.3ae | 10GBASE-LR | 10km |
| 10 Gbps | Single-Mode | 802.3ae | 10GBASE-ER | 30km |
## UTP vs Fiber-Optic Cabling
- UTP
- Lower cost than fiber optic.
- Shorter Maximum distance than fiber0-optic (100m).
- Can be vulnerable to EMI
- RJ45 ports used with UTP are cheaper than SFP ports.
- Emit (leak) a faint signal outside of the cable, which can be copied (= security risk)
- Fiber-Optic
- Higher cost than UTP.
- Longer maximum distance than UTP.
- No vulnerability to EMI.
- SFP ports are more expnsive than RJ45 ports (singl-mode is more expensive than multimode).
- Does not emit any signal outside of the cable (=no security risk)

118
03. How the TCPIP Model Actually Works.md Normal file
View File

@@ -0,0 +1,118 @@
---
id: 03. How the TCPIP Model Actually Works
aliases: []
tags:
- CCNA
---
# How the TCPIP Model Actually Works
## Protocols and Standards
A [[Protocol]] is a set of rules defining how data should be communicated between devices over a [[network]].
- The "Languages" that computers use to communicate.
Since the early days of computer networking, there have been several attempts to define the functions needed for computers
to communicate with each other
- Often developed by a specific vendor (e.g, [[IBM]]) to be used with their own products.
- With a proprietary approach, enabling communications between different vendor's products was difficult.
A [[standard]] is an agreed-upon specification that describes how a protocol or technology should work
- With vendor neutral standards, devices of all types can communicate with each others.
- An [[Apple]] Macbook can access a [[website]] hosted on a web server running [[Linux]].
- A PC running [[WIndows]] can send an email that can be read on a smartphone running [[Android]]
## A bit of history
Early work on the computer netowrks that would evolve into today's [[Internet]] began in the [[1960]]s
- The [[US]] Department of Defense's [[ARPA]] funded ARPANET, which came online in 1969 to connect mainframes at universities and labs
- Originally used a protocol called [[NCP]]
Vint Cerf and Bob Kahn (working on DARPA) began developing [[TCP]] in 1974
- Later divided into two protocols still used today:
- [[TCP]]
- [[IP]]
THese two protocols form the fundation of the protocol suite known as [[TCP/IP]] today
- ARPANET fully switched to TCP/IP in January 1, 1983.
TCP/IP became dominant over vendor-proprietary solutions at the time because it was published as a set of open
standards that any vendor could implement, and it could run over many different types of networks.
## Who defines the standards?
Most netwoking standards are developed by independent standards organizations, not by a single vendor, with participation from engineers at many companies
- [[IEE]] (Institute of Electrical and Electronics Engineers)
- Develops many of the technologies used on local area netowrks:
- [[Ethernet]] (802.3)
- [[WIFI]] (802.11)
- [[IETF]] (Internet Engineering Task Force)
- Open community that defines [[protocols]] used on the [[Internet]]
- [[TCP]], [[IP]], [[UDP]], [[HTTP]], [[DNS]], etc.
- Publishes standards in document called [[RFC]]'s (Requests for Comments)
## Layered models
Networks do a lot of different jobs to move data from one computer to another.
- Physical transmission of signals, local delivery on a [[LAN]], routing traffic between networks, end-to-end conversations, applications, etc.
A model lets us group related jobs into layers.
- Each layer has a specific role.
- Each layer uses the services of the layer below and provides services to the layer above
Protocol live (mostly at one layer)
- Examples later: IP, TCP, HTTP, etc.
- Together they form a stack of protocols that work as a team (the network stack)
1. Application Layer : telnet, FTP, TFTP
2. Transport Layer: TCP, UDP
3. Internet Layer: IP, [[ICPM]]
4. Link Layer: cables, WIFI
The model is description, not a law.
- Different textbooks/courses use slightly different models (4-layer, 5 layer...)
## TCP/IP Layers
### Layer 1 : the physical layer
- The physical Layer (Layer 1) sends and receives bits as electrical, optical, or radio signals over the medium
- Defines things like cables, connectors, signal levels, and link speeds.
- Examples: copper UTP cables, fiber-optic cables, WI-FI radios and antennas, network interface cards [[NIC]]'s
- The physical aspects of transmitting data are very complex
### Layer 2 : Local Network Layer
- The Local Network Layer provides hop to hop delivery of messages on a local network.
- A hop is one step along the path between two devices:
- From one router or host, to the next router or host in the path
- [[Switches]] don't countL a switch just extends the local network, allowing multiple devices to connect.
- Uses [[MAC]] addresses to identify interfaces.
- Protocols at this layer includes
- Eternet
- Wifi
### Layer 3 : The Internet Layer
- The Internet Layer provides end-to-end delivery between hosts across multiple networks
- Uses IP addresses to identify hosts in the network.
- Routers operate mainly at this layer, using the message's destination IP address to forward the message toward its final destination host
- Protocols at this layer includes
- IP ([[IPv4]], [[IPv6]])
- [[ICMP]]
### Layer 4 : The Transport Layer
- The Transport Layer provides end-to-end communication between application processes.
- Also called "process to process" or "service-to-service"
- Uses port numbers to identify the processes on each host.
- Runs mainly on the communicating hosts; routers normally operate based on IP, not on Transport layer informations
- Protocols at this layer includes
- UDP
- TCP
### Layer 5 : Application Layer
- The application Layer is where network communications meet applications.
- Usually called Layer 7
- Defines how application processes format, send, and interpret data
- Protocols at this layer define message formats and rules for specific tasks, such as:
- [[HTTP]]/[[HTTPS]]
- [[FTP]], [[TFTP]]
- [[SMTP]], [[POP3]] , [[IMAP]]
- Network infrastructure devices (routers, switches) don't care about Application-layer details.
- They just move messages across the network.
- Only the communicating hosts interpret the data

177
04. Intro to the CLI.md Normal file
View File

@@ -0,0 +1,177 @@
---
id: 04. Intro to the CLI
aliases: []
tags:
- CCNA
---
# Intro to the CLI, Introduction to the [[CISCO IOS]]
## How to connect to a [[Cisco]] device
connect via a console port with [[RJ45]] or [[USB-mini]]
Use a Rollover cable
## Terminal Emulator
access with a Terminal Emulator (ex: PuTTy)
default configuration:
speed: 9600
data bits: 8
stop bits: 1
parity: none
flow control: none
## user Exec Mode
User Exec mode is very limited.
Users can look at some things, but can't make any changes to the configuration.
also called 'user mode'
```Cisco
Router>
```
## Privileged Exec mode
Provide complete access to view the device's configuration, restart the device, etc..
Cannot change the configuration, but can change the time on the device, save the configuration, etc...
```Cisco
Router>enable
Router#
```
## ? "list command available"
for the full list of all the command available just type *?*
```Cisco
Router>?
Router#?
// to display abiguous command
Router>e?
enable exit
```
## Global configuration mode
To enter configuration mode
```Cisco
Router#configure termianl
Router(config)#
//shortcut
Router>enable
Router#con?
configure connect
Router#conf t?
terminal
Router#conf t
Router(config)#
```
## Enable password
To enable password in the config mode
**passwords are case-sensitive**
if you type 3 time a false password it exit
```Cisco
Router (config)# enable password |your password|
// ex:
Router (config)# enable password CCNA
Router (config) #exit
Router>enable
Password:
Router#
```
## Running-config / startup-config
There are two separate configuration files kept on the device at once.
- *Running-config* : the current, active configuration file on the device.
As you enter commands in the CLI, you edit the active configuration.
- *Startup-config* : The configuration file that will be loaded upon restart of the device.
### Show running-config/ show startup-config
```Cisco
Router#show running-config
Router#show startup-config
```
## Saving the configureation
there are three ways to save the running configuration to the startup-config
```Cisco
//1.
Router#write
//2.
Router#write memory
//3.
Router#copy running-config startup-config
```
## Service password-encryption
for security purpose always save the password with password-encryption enable
```Cisco
Router (config) # service password-encryption
//when using the show running-config it return
enable password 7 |hash of the password|
```
note: the number 7 is the type of encryption used for the encryption
7 is the proprietary Cisco encryption [[algorithm]]
with the first method is easy to decrypt the password with a deencryption tool
## Enable secret
for more security use the method enable secret
```Cisco
Router (config) #enable secret |Your password|
ex:
Router (config) #enable secret Cisco
//when using the show running-config it return
enable secret 5 |hash of the password|
```
note : number 5 is the number for the [[MD5]] encryption
### sercice password-encryption
if you enable service password-encryption
- current passwords will be encrypted
- future passwords will be encrypted
- the enbalbe secret will not be effected
if you disables service password-encryption
- current passwords will not be decrypted
- future passwords will not be decrypted
- the enable secret will not be effected
## Canceling commands
for canceling a command with the device type *no* + the name of the command
```Cisco
Router (config) #no service password-encryption
```

111
05. Ethernet LAN Switching.md Normal file
View File

@@ -0,0 +1,111 @@
---
id: 1772845705-JEBL
aliases:
- Ethernet LAN Switching
tags: []
---
# Ethernet LAN Switching
## [[OSI model]] - physical layer
- Defines physical characteristics of the medium used to transfer data between devices
- For example, [[voltage]] levels, maximum transmission distances, physical connectors, cable specifications, etc..
- Digital [[bits]] converted into electrical (for wired connections) or radio (for wireless connections) signals
- All of the information in day 2 [[02. Interfaces and Cables]] (cables, pin layout, etc.) is related to the Physical layer.
## OSI model - Data Link Layer
- Provides node-to-node connectivity and data transfer (for example, PC to switch, switch to router, router to router)
- Defines how data is formatted for transmission over a physical medium (for example, copper UTP cables)
- Detects and (possibly) corrects Physical Layer errors.
- Uses Layer 2 addressing separate from Layer 3 addressing
- Switches operate at Layer 2.
## OSI Models - PDUs
Layer 4 header - Data
Layer 3 header - Segment
Layer 2 header - Packet
Layer 1 header - Frame
Protocol Data Units | PDUs
## Ethernet Frame
ethernet header | Packet | Ethernet Trailer
### Ehternet Header
Preamble | Start Frame Delimiter (SFD) | Destination | Source | Type or Length
7 bytes 1 byte 6 byte 6 byte 2 bytes
#### Preamble
- Length : 7 Bytes (56 bits)
- Alternating 1's and 0's
- 10101010 * 7
- Allows devices to synchronize their receiver clocks
#### SFD
- Start Frame Delimiter
- Length: 1 byte (8 bits)
- 10101011
- Marks the end of the preamble, and the beginning of the rest of the frame
#### Destination & Source
Indicate the devices sending and receiving the frame
- Consist of the desination and source [[MAC Address]]
- MAC = Media Access Constol
- = 6 byte (48-bit) address of the physical device
#### Type / Length
- 2 byte (16-bit) field
- A value of 1500 or less in this field indicate the LENGTH of the encapsulated packet (in bytes)
- A value of 1536 or greater in this field indicates the TYPE of the encapsulated packet (Usually [[IPv4]] or [[IPv6]])
and the length is determined via other methods
IPv4 = 0x0800 ([[hexadecimal]])
(2048 in decimal)
IPv6 = 0x86DD (hexadecimal)
(34525 in decimal)
### Ethernet Trailer
Frame Check Sequence (FCS)
4 bytes
#### Frame Check Sequence
- 4 bytes (32 bits) in length
- Detects corrupted data by running a 'CRC' algorithm over the received data
- CRC = Cycling Redundancy Check
## Mac Address
- 6-byte (48-bit) physical address assigned to the device when it is made
- AKA ' Burned-in Address' (BIA)
- Is globally unique
- The first 3 bytes are the OUI (Organizationally Unique Identifier), which is assigned to the company making the device
- The last 3 bytes are unique to the device itself
- Written as 12 hexadecimal character
Unicast frame: a frame destined for a single target
### Dynamically learned Mac Address
Is a mac address learned by the switche automatically by looking at the frame Destination Frame
if the Mac address is not in the switch mac address table it will flood the frame (send the frame at all the interfaces except the source mac address)
until the PC replied to another pc
**Unknown Unicast Frame** -> *Flood*
if the Mac address is knowned by the switch it will directly send it in the interface
**Known Unicast Frame** -> *Forward*
*Dynamically Mac Addresses are removed from the MAC address table after 5 minutes of inactivity*

17
README.md
View File

@@ -1,16 +1,9 @@
# CCNA Notes
All my notes for passing the CCNA exam
All my notes for passing the CCNA exam (based on Jeremy ’s IT Lab)
The **Cisco Certified Network Associate (CCNA)** is a
widely recognized entry-level IT certification that validates
a professional’s understanding of networking fundamentals.
It covers key topics such as network access, IP connectivity,
security basics, automation, and troubleshooting.
CCNA is designed for individuals starting a career in
networking and provides a strong foundation for roles like network technician,
support engineer, or junior network administrator.
This repository contains my structured notes from studying
the Cisco Certified Network Associate (CCNA) using Jeremy's IT Lab.
It covers essential networking concepts including network fundamentals,
IP connectivity, network access, security basics, automation, and troubleshooting.
## Free CCNA 200-301 Complete Practical Course V1.1 by David Bombal Tech
[Link to the video](https://youtube.com/playlist?list=PLw6kwOJVj3MbMZ8B72ZgUryj8OSETC0ds&si=8JAireGwkWrVzHbe)