Cisco CCNA



Hey All.

Im Currently teaching a friend of my the glorious world of Cisco so he can attempt for CCNA and instead of teaching 1 person i figured why not teach loads!! so as i go through the topics i will post the study notes on this thread as to be honest not many people know what cisco is!!

Anyway i hope you enjoy i will post up what i will be running through in the next day or 2


Section 1 - Networking Fundamentals (ICND1)
Lecture 1: Networking Fundamentals and the OSI Model
Lecture 2: Networking Layer Interaction and More!
Lecture 3: Fundamentals of Network Troubleshoot Models
Lecture 4: The Fight of the Century: TCP vs UDP
Lecture 5: More TCP, UDP and Port Numbers

Section 2 - Ethernet (ICND1)
Lecture 6: Duplexes, Suplexes and Autonegotiation
Lecture 7: Cabling Types and Standards
Lecture 8: Formats and Rollover Cables
Lecture 9: Show Interface Ethernet

Section 3 - Switching 101 (ICND1)
Lecture 10: Hubs and Repeaters (Yes we have to talk about this :( )
Lecture 11: The Dawn of Switching
Lecture 12: Building a MAC Address Table (The Smart Way)
Lecture 13: Let the Switch do the work : Dynamic MAC Address Table Entries
Lecture 14: How they get there: Frame Forwarding Meathods
Lecture 15: The Joys of VLANs
Lecture 16: The Cisco Switching Model and Intro to Port Security
Lecture 17: Port Security Secure MAC Addresses
Lecture 18: Port Secruity Sticky MAC Addresses
Lecture 19: Combining Secure and Sticky MAC Addresses
Lecture 20: Spanning Tree Protocol Fundamentals
Lecture 21: What Do Those Lights Mean?
Lecture 22: Trunking Fundamentals
Lecture 23: Trunking Labs and Modes
Lecture 24: Drawing The Line: Allowing and Disallowing VLANS
Lecture 25: VTP Fundamentals
Lecture 26: Resetting the revision number: What is the big deal?

Section 4 - A QUick WAN Intro (ICND1)
Lecture 27: Exactly the section name a quick intro to WAN!!

Section 5 - Routing and IP Addressing Fundamentals (ICND1)
Lecture 28: A First look at Routing
Lecture 29: IP Address Range, Classes and Why we care?
Lecture 30: Routing PRocesses and Walkthroughs

Section 6 - Cisco Configs, Memory and More! (ICND1)
Lecture 31: "Thanks for the memories"
Lecture 32: Encryption (And Setup Mode)
Lecture 33: My States of the interface speech
Lecture 34: Startup and Running Configs and the COPY Command
Lecture 35: The Config Registry and Real-World Password Recovery

Section 7 - DNS, ARP, and DHCP (ICND 1)
Lecture 36: DNS And ARP
Lecture 37: Proxy ARP And DHCP Fundamentals
Lecture 38: DHCP Relay Agents and IP Helper Addresses
Lecture 39: Using A Cisco Router As A DHCP Server

Section 8 - Passwords, Banners, Telnet, and More! (ICND 1)
Lecture 40: Configuration Mode Review
Lecture 41: Important Cisco Router Defaults and the Console Port Password
Lecture 42: Telnet Fundamentals and Lab
Lecture 43: SSH Lab
Lecture 44: Enable Secret vs. Enable Password
Lecture 45: More Telnet Lab and "Priv Level 15"
Lecture 46: Banner Labs
Lecture 47: Logging Synchronous, Exec Timeout, And A History Lesson
Lecture 48: A Little More Telnet
Lecture 49: A Voyage Of (Cisco) Discovery

Section 9 - Static Routing And A Little DV (ICND 1)
Lecture 50: Static Routing Fundamentals
Lecture 51: Static Routing Lab And IP Debugs
Lecture 52: More Static Routing With A Side Order Of DV Protocols

Section 10 - OSPF And Link-State Protocols (ICND 1)
Lecture 53: Wildcard Masks
Lecture 54: Link State Protocol Fundamentals
Lecture 55: OSPF Debugging, Troubleshooting Adjacencies Lab 1
Lecture 56: More Troubleshooting, Plus Hello And Dead Timers
Lecture 57: The Process ID
Lecture 58: Show IP OSPF Interface Details and the OSPF RID
Lecture 59: The Default-Information Originate Command (And Options!)
Lecture 60: The When, Why, And Where Game: Passive Interfaces


Loool ur so geeky!! :) thank you though im actually interested for this!


I got my CCNA from IT Carlow last year in first year. Very interesting subject :)


Lecture 1: Networking Fundamentals and the OSI Model and part of Lecture 2: Networking Layer Interaction and More!

Right before we jump into the glorious world of networking, we need to ask ourselves what is networking.

Why are we doing all this stuff with Switches, Routers, Hubs and who knows what else!!

Well yes that is 2 questions, but you get the point…. Networking was once very very simple. We had a few end users with terminals and a printer… and well that was about it!

People were so fascinated of the idea that 10 different people could send data to that one printer from the other side of the room and it would work, they just found it fascinating!!

But of course humans being humans, we got bored of that after a while and though well what else can we do? And that’s where it started to get complicated. Companies went from wanting to transfer files from person to person, to being able to save data to one central location to wanting to hold voice conferencing… we turned the fantasies people had when the first computer networks came about, services that we can use today without a second thought into reality. Networks have grown and grown and grown in order to handle these services and make them available to our end users in an efficient manner.

And then of course we wanted to secure our networks which made things get a little bit more difficult and can make the way a network operates more complicated….

In short we have a collection of devices that can be put together to make up a network like the ones shown below and it’s our job to get them to work together!!

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If you’re new to networking you probably haven’t heard of a lot of these devices and it can be very daunting, I remember my first job in the industry walking into a server room and all the flashing your lights and just thinking what the hell is all this, it is very intimidating!!
And the key to success in the field is it’s all about the fundamentals, success in networking whether it be in the exams or in a server room is all about knowing and applying the fundamentals. They are probably the most important things to know throughout the whole CCNA!!!
I’m mentioning this now for one reason and trust me because I thought the same thing, one day if you decided to take a path in cisco you will be studying and sat there thinking Do I REALLY need to know the fundamentals are, do I really need to know the OSI model….. YES YOU DO!!!!

You’ll see why as we dive into the material more and more so let’s get too it!!!

The OSI Networking Model

The OSI model isn’t just something to remember for the exam and then forget. Its something youll find useful for real-world troubleshooting and for breaking networking down into pieces that are easier to learn, I just it on pretty much every job I go on!!

We’ll first take an introductory look at the OSI mode, getting familiar with what’s going on at each level, and then we will use it to create a path for CCENT and CCNA exam success depending on which route you go for!!
Here is the OSI Model

Data Link

As network administrators our primary concern is with the bottom three layers. But as CCENT and CCNA candidate, we are concerned with all seven layers as they will be in the exam so we will start at the top and work our way down

The Application Layer
The Application layer is where out end users interact with the network.
It performs important behind the scenes tasks such as:
Makes sure the remote communications partner is available
(Remember it takes two to network)

Ensures that both ends agree on a myriad of rules including data integrity, privacy and error recovery

The Presentation Layer
This layer answers one basic question…. How should this date be presented?
Ever opened a PDF file with a non-PDF-Friendly word processing app? You end up with hundreds of lines of unreadable rubbish that you don’t understand, that’s a presentation layer issue
Encryption takes place at this layer, you’re going to hear a lot about encryption later!

The Session Layer
This layer is the manager of the overall data and transfer process. It handles the creation, maintenance, and teardown of the communication channel between two parties

The Transport Layer
The main purpose of the Transport layer is to establish a logical end-to-end connection between two systems.
That’s not the only this going on here! Most oft eh additional transport layer functions involve either the Transmission Control Protocol (UDP) or the User Datagram Protocol (UDP), thos two protocols are so important that they have their own sections on the exam!! (A section can be worth 100+ points on the exam so I’ll explain in a lot of detail!!)
Now we come to the OSI layers you will mainly work in as Network Admins/Consultants in the working world.

The Network Layer
For the router, the network later processes answers tow basic questions:
What valid path exists from here to point B?
Of which of those paths is the best to get there
And that’s about it!!
Of course it’s not that easy, we will dive into the details later at the moment, it’s enough to know that ip addresses ( for example) are used at the routing layer.
There’s another important address we use in our networks and that is in the next layer

The Data Link Layer
We’ll be spending A LOT of time with switches, and our switches run at this layer, as do these protocols:
HDLC (High Data Link Control)
PPP (Point-to-Point Protocol)
Frame Relay
This address running at this layer is known as the MAC address, but it had four other names you will need to know as they don’t always call it the MAC in the exam, they are:
Layer 2 address
Hardware address
Burned-in address (BIA)
Physical address
You may be wondering the same as I did, why does it need all these names???.... Well the first name makes perfect sense since we are at Layer 2, but what about the others?

This address is actually burned into the hardware so you see where the “hardware and Burning in” names come from. Be careful with the last name though. We sometimes call the MAC address the physical address because it physically exists on the hardware NOT because it runs at the physical layer of the OSI model because it doesn’t!!
Right now I want to introduce you to a set of terms that sound like they do the same thing, but we need to be very clear on the difference:
Error detection Error Correction
Remember: Detecting something doesn’t mean you’re correcting it.
Here why in bringing it up!!
The data link layer performs error detection via the frame check sequence (FCS). The actual operation of the FCS goes beyond the scope of the CCENT exam, but as network admins you really should know the FCS fundamentals:
  1. The sender runs a mathematical formula (an algorithm) against the contents of the frame.
  2. The sender places the result of that value in the FCS file of the frame, and then sends the frame
  3. The receiver of the frame runs the same algorithm against the contents of the frame, if the result value matches the contained FCS field, the frame is fine. If that resulting value doesn’t match the frame is considered corrupt and deleted.
    So why no error recovery? It’s the recipient of the frame that detects the error, not the sender and the recipient can’t retransmit the frame to itself. All the recipient can do is let the sender know there was a problem
The Physical Layer
All the work we do at the upper layers of the OSI model is all about sending data across the physical layer in the form of ones and zeroes.

The data our end users create is going to be eventually translated into 1s and 0s. Anything having to do with a physical cable or the standards in use – the pins, connectors and the actually electric current – is running at the physical layer
With our end users entering data / sending photos /watching videos or whatever, it sound like we have a lot of work to turn all of that into ones and zeroes
It’s almost like we need a plan… well here it is!!


The Date Chopping Process
This is actually knows as the overall data transmission process. It’s also a good reminder for network newcomers as to what were actually doing here.

When the end user sends data, the data goes through all seven layers of the OSI model, but it doesn’t keep the same form otherwise the physical layer would be getting HUGE chucks of data and have no idea what to do with it.

Instead the Transport layer begins the process of taking the data and segmenting it into smaller units, and each layer below the Transport layer will break the units up into even smaller units, until the data has been transformed into a stream of ones and zeroes that can successfully be transmitted by the Physical layer.

I can guarantee the following data unit terms and their associated OSI layers will show up in the exams.
At the Application, Presentation and session layers, data is simply referred to as “data”. While there are important operations going on at these layers, the “chopping” of the data hasn’t started yet.

The process begins at the Transport layer, where the data is placed into segments.

At the Network layer, the data is placed into packets.

At the Data link layer the data is placed into frames

Finally at the Physical later, data takes the form of bits, and those bits are all ones and zeroes.

For your exams, be very clear about the transmission unit associated with each OSI layer.

There’s a little extra overhead involved with the OSI mode. Each layer is going to add its own header that will be removed by the same layer on the other end of the session. These headers are layer-specific. The Transport layer doesn’t care about the contents of any header except the ones placed by the Transport layer on the other end of the session

There are almost always exceptions in networking. Each of the top six layers will place only a header on the data except for the Data Link layer, which will add both a header and a trailer

*insert pic------
This combination of data and a layer-specific header is a Protocol Data Unit (PDU) and there’s a PDU for each layer shown above. There usually referred to by the layer – L7 PDU, L6 PDU etc.

Once the data is successfully transmitted by the physical layer, the data flows back up the model on the other end of the session. As you’d expect, each layer removes the header added by its counterpart on the other end of the session (Same layer interaction)

---- Insert pic----

We will do a quick comparison of same-layer and adjacent layer interaction

“Same-layer interaction” refers to an OSI layer on one end of the session removing the header placed on it by the same layer at the other end of the session”
-------Insert pic------

Adjacent-layer interaction refers to the interaction between layers of the OSI model on the same host.
For example the application layer can have adjacent-layer interactions with the presentation layer, the presentation layer can have adjacent-layer interaction with both the application and session layers (the ones directly above and below it) and so forth.

Anyway that’s enough of the OSI for now, next up will be the networking model!!!


this is very good i actually wish I had this when I was studying all this stuff lol


The TCP / IP Networking Model
This model also uses layers to illustrate the data transport process, but only five layers as opposed to the OSI model’s seven.
For the CCENT and CCNA exams, it’s an excellent idea to know the following:
  • The layers of the TCP/ IP and OSI models (check!)
  • The responsibilities of each layer (check!)
  • How the layers of the two models map to each (coming up!)
Here’s the latest version of the TCP/ IP model!
Data Link

Let’s map the OSI model to the TCP model:
Presentation Application

Transport Transport
Network Network
Data Link Data Link
Physical Physical

The Application layer of the TCP/ IP model maps to the top three layers of the OSI model (Application, Presentation, Session). After that, it’s a one-to-one layer mapping all the way down.

You TCP/ IP model veterans know this is a LOT easier to deal with than the previous model, which follows:


The Internet layer is bulging a little bit, since I wanted to put at least two of the known names for that layer in there. Don’t even get me started on the multiple names there have been over the years for the bottom layer. We’re all happier with the new TCP/ IP model.

There’s nothing tricky about these models, and they will be easy points for you on exam day. Having said that, on exam day, quickly double-check any questions you’re given on these models to be sure of the model you’re being asked about.

If you’re asked about the OSI model, don’t give an answer of a layer in the TCP/ IP model.

Here’s the magic question a lot of people are thinking when reading this:
Why Do We Use Models, Anyway?

One reason is that networking models help software vendors create (we hope) interoperable products.

For our purposes, breaking the overall networking process into smaller pieces makes it a lot easier to learn networking in the first place.

This is a very important point, not just for this section, but for all of your studies – Cisco and otherwise. It’s really easy to become overwhelmed when you start learning this stuff.

Here’s a certain cure for that feeling: Just take it one feature at a time. Learn one thing about the subject matter at a time, and soon you’re got it all mastered.

That’s worked for me and it’ll work for you, too.

Now back to the “why” regarding these models…

Using a networking model to structure your troubleshooting approach is a real help, especially since most of what you and I do as network admins is troubleshooting. (It’s not like we configure our networks from scratch every single day.)

Its always best to start at the Physical layer, and you’ll see what I mean as we perform troubleshooting throughout the course. In my experience, there are two kinds of network troubleshooters:
1. Those who have a structured approach.
2. Those who don’t have a structured approach, and are basically just trying things blindly because they don’t truly understand what they’re doing.

You want to be #1.

In short – or in long – these networking models aren’t just something to memorize for your exams. You’ll be using them throughout your career, even if you’re not consciously thinking about it.