Chapter 3: Models

Note: I have discontinued this blog. Instead I have started a FREE video series on CCNA in YouTube. You can find it here. 

Models???

Yes, Models. You cannot go for long in the networking industry, before somebody says, 'Oh that is Layer 1 functionality' or 'Check the Layer 3 devices'! What does it mean when somebody says Layer 1 or Network Layer in the networking field? Well that is what we will learn in this chapter!

Tell me more!

In the mid 70s, when the networks first came into being, a computer could communicate only with another computer of the same manufacturer! With different manufacturers around, this was something that did not have a future! In the late 1970, Open Systems Interconnection (OSI) reference model was created by International Organisation for Standardization (ISO) to break the barrier.

The main aim of the OSI was to help vendors create interoperable network devices and software, that could be used by all manufacturers! This was a boon for users' as well, so that they did not have to be locked in with a particular vendor!

Ah I see, but I thought you said 'LAYERS'...

Yes! The basis for OSI was a layered approach. OSI reference model was a conceptual blueprint on how communication should take place. It addresses all the process required for communication and divides them into logical groupings called as Layers!

As an analogy, we can compare it to a large company with different departments! Each department has their own functions and their role. For the company to run smoothly, each department must trust and rely on information being passed from other departments. Similarly, each layer has its own functions. The adjacent layer, will rely on the functions/outputs of any layer, without bothering how it functions or gets the output. This inherently gives manufacturers and developers flexibility to change their design or code any time, but making sure the output remains unchanged!

Interesting.... so what do you reckon are the advantages of a layered approach?

As mentioned above, there are lot of advantages. Just to list a few:

1. It divides the network communication process into smaller and simpler components
2. It allows multiple-vendor development through standardization of network components
3. It encourages industry standardization by defining what functions occur at each layer of the model
4. It allows various types of network hardware and software to communicate
5. It prevents changes in one layer from affecting other layers, so it does not hamper development

Let us see the OSI Reference Model in brief!

As mentioned earlier, it was a model created by ISO. It has 7 layers as mentioned below:

Application (Layer 7)

Presentation (Layer 6)

Session (Layer 5)

Transport (Layer 4)

Network (Layer 3)

Data Link (Layer 2)

Physical (Layer 1)

As a network engineer, you will only be bothered about the last 4 layers. The top 3 layers are to be concerned with the computer system. Nevertheless, we will try to understand the functioning of all the layers. I cannot stress this enough, but remember - OSI Model and the TCP Model is the very basic fabric of your networking career! Get this concept right, and you will fly through your networking career!

Application Layer:

This layer comes into play, when a computer needs to access the network! This is where all the user actions happen. For example, if you uninstalled all network components of your pc like TCP/IP, NIC card and so on and use Internet Explorer to view local HTML document, then Application Layer WILL NOT come into picture. But the moment you ask it to fetch a document or a website from the internet, the application layer is kicked into action. Protocols like HTTP, FTP, TFTP, TELNET and so on are used by the application layer to take information down to other layer functions.

Presentation Layer:

This layer gets its name from its function: Presenting data to the Application layer or formatting data for the Sessions layer. This layer is essentially a translator and provides coding and conversion functions. A successful data transfer technique is to adapt the data into a standard format before transmission. This ensures that all the data going to lower functions, are formatted exactly the same way, across all system including the ones manufactured by different manufacturers!

Session Layer:

This layer is responsible for setting up, managing and then tearing down session between presentation layer entities. That means, if you open a web browser and also uploading files through FTP, the session layers maintains separate session for each of these protocols. It also co-ordinates communications between systems and servers to organize their communication, by offering three different modes: simplex, half-duplex and full-duplex!

NOTE: Layers from here down are crucial for a Network Engineer!

Transport Layer:

This layer is responsible for segmenting data going down and reassembling data going up! It also sequences each segment, so that it can reassemble each of them in the correct order! At this layer, an application can choose between TCP (Transmission Control Protocol - which is reliable) or UDP (User Datagram Protocol - which is UNreliable). TCP is more reliable because it makes uses of flowcontrol, windowing and segment acknowledgement. It is used for more secure level of communication. Whereas UDP does not have acknowledgement and is used as a best effort delivery. This is used in realtime applications like voice chats and video chats (this is why you see missed pixels on your video chats)!

From a CCNA perspective, Cisco expects you to know only about TCP. Hence we will look closely at TCP.

TCP is used for Connection-Oriented Communication. Before they start communicating, they need to establish a connection which is also sometime referred to as THREE WAY HANDSHAKE! It works as described in the diagram below:

As we can see from the diagram, the first machine sends a SYN signal to the second machine. When it receives the SYN, it sends back a SYN-ACK to the first machine. The first machine then sends an ACK back. At this point their connection is said to be established and they can start sending data.

TCP also uses a concept known as FLOW CONTROL to make sure that data transmission is secure. It is as given in the following diagram:

After sending each segment, the sender waits for an acknowledgement from the receiver. If it receives, the acknowledgement it sends the next sequence. But if it doesn't get an acknowledgement within the specified time, it resends the sequence. The segments are sequenced in the proper order at the receiving end.

To make this process even more efficient, a concept called WINDOWING was introduced. As per this concept, instead of the sender waiting after sending just one segment, it sends more segments as per the WINDOW size of the receiver. If it receives all the segments, it send just ONE acknowledgement stating the next segment it is expecting. If at all one or more segments are lost in transmission, and the receiver does not get that, it will send ACK for that segment. The sender will only send the lost segment. This concept will become more clear with the following diagram:

Network Layer:

Network layer is responsible for tracking where the devices are on the network, manages device addressing and determines the best way to move data. Routers are specified at this layer and provide the routing services within an internetwork. This is the layer that is concerned with IP ADDRESSES.

When a router receives a segment, it breaks it into packets and adds headers. It then checks its routing table to see if it knows a route to the destination network. If it knows, it just forwards the packet to the interface of the router through which it can reach the network. If it doesn't it just drops the packet. 

There are two types of packets:

1. Data Packets - Used to transport data through the internetwork. Protocols used to support data traffic are called Routed Protocols 
2. Route Update Packets - Used to update neighbouring routers about the networks connected to all routers within the internetwork. Protocols that send route updates are called Routing Protocol

We will learn more about Routers and protocols in later chapters.

Data Link Layer:

This layer provides physical transmission of the data and handles error notification, network topology and flow control. This layer is concerned with MAC address and delivery of message to the proper device on LAN using MAC addresses.

This layer also breaks down the Network Layer packets into smaller sections called Frames and adds its headers. At this layer a footer is also added.

This IEEE Ethernet Data Link layer has two subsections:

1. Media Access Control (MAC) 802.3 - It defines how the packets are placed on the media. It is always a 'first come first serve' access where everyone shares the bandwidth.
2. Logical Link Control (LLC) 802.2 - Responsible for identifying Network Layer protocols and encapsulating them. 

Switches and bridges work at this layer.

Physical Layer:

This layer is the last layer down (or layer 1 in naming convention). This is layer that is actually concerned in transmitting the bits and receiving them. The physical medium can be anything, like Ethernet cables, fibre optic cables, wire less, or any other medium. They all have their protocols to make sure data is encapsulated according to their requirement at one of the upper layers.

This layer specifies the electrical, mechanical, procedural and functional requirements for activating, maintaining and deactivating a physical link between end systems. This layer is also where you identify between DTE (Data Termincal Equipment) and DCE (Data communication Equipment). The physical layers connectors and different topologies are defined by the OSI standards.

And what about The TCP Model?

Well the TCP Model is derived from the OSI model, and is the model that is more relevant to a network engineer. Some of the layers in OSI has been combined to form a single layer. The TCP layers are:

1. Application Layer:  HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP
2. Transport Layer:  TCP, UDP, RTP
3. Internet Layer:  IP, ICMP, ARP, RARP
4. Network Access (Interface) Layer:  Ethernet, Token Ring, FDDI, X.25, Frame Relay, RS-232, v.35

The functions of layers of OSI and TCP are quite similar, except that some have combined together. Hence I have just listed all the protocols in each layer.

A comparison summary is as given in the diagram below:

The following diagram explains data flowing through the layers, with headers being added at each layer.

As seen, on the way down headers are added and the data starts growing and on the way up at the receiving end, the headers and trailers are stripped away to finally receive the original DATA.

Summary

We have learnt models today. Let us summarize:

1. Definition of Models
2. Why is a layered approach necessary?
3. Understanding of the OSI Model and its protocols
4. Understand the TCP Model and protocol
5. Comparison between the models
6. Understand how the data flows through the model

Fastest Finger First

A) OSI Model is a ..........

1. Physical Model
2. Real Model
3. Reference Model
4. IEEE Model

B) Application layer protocols are ...........

1. HTTP
2. TELNET
3. FTP
4. All of the above

C) TCP is a .........

1. Connection-less protocol
2. Connection-oriented protocol
3. Unsecure protocol
4. All of the above

D) The 4 layer is.......

1. Session
2. Network
3. Transport
4. Presentation

Thank You!

If you have any queries, post it as a comment below. I will answer all your queries. Also as soon as you complete today's class, give the correct answers for FASTEST FINGER FIRST in the comment section below.

Chapter 2: Internetworking Basics

Note: I have discontinued this blog. Instead I have started a FREE video series on CCNA in YouTube. You can find it here. 

Alright, yesterday we saw a bit about networks and IP Addresses. Today we will see in detail how a network device communicates with each other.

Before we start, let us define COMMUNICATION.

What is communication?

Good Question.... well...

DEFINITION TIME: Communication is the process where two or more devices pass information between themselves and is accepted.

Communication can be divided on the basis of destination.

1. Unicast ---> One to One
2. Multicast ---> One to Many
3. Broadcast ---> One to ALL

Based on characteristics of communication, it can be divided as:

1. Simplex ---> Communication possible only in one direction
2. Half Duplex ---> Communication possible in both direction, but only one device at a time
3. Full Duplex ---> Communication possible in both direction simultaneously

Let us start by taking a very basic network with a hub and two PCs as given in the diagram below:

DEFINITION TIME: A HUB is a multi-port repeater, sending out the same signal onto all the other ports.

Lets assume Jack wants to say a HELLO (or whatever packet of information) to Jill. What do you think Jack will do? Any guesses? Did you say it will send HELLO to the Hub addressed to Jill? NO. Then? Do you think it will send HELLO to Jill's IP Address? Sorry Again! Actually the answer: To its MAC address! A hub works on the physical layer (Layer??? Dont worry, we will talk a LOT about layers in tomorrow's chapter!)

MAC Address, what is that?

DEFINITION TIME: A MAC (Media Access Control) Address is the hardware address. It is also called Burn-In-Address. This address cannot be changed and is unique to the NIC. It is a 48bit HexaDecimal number

Right... so how does Jack communicate with Jill? If Jack know's Jill's MAC Address, it just sends the message to Jill's MAC address. If it knows only Jill's IP Address or hostname, it can send a broadcast, asking Jill for her MAC address! Jill receives the broadcast and sends a reply back to Jack with her MAC address. Jack then uses that information and sends the message to Jill.

With this given configuration (connecting through a hub), it is a pointless exercise, because even after addressing the message to Jill's MAC address everybody connected to the hub will receive the message! 

This is because a hub has only one Broadcast Domain and one Collision Domain.

What is a Broadcast Domain and a Collision Domain?

DEFINITION TIME:  

Broadcast Domain is the space on the network where a broadcast reaches

Collision Domain is the space where only one device can communicate at a time

So if two or more devices connected to a hub, communicates at the same time then a collision occurs. So as more and more devices get connected to the HUB, the network will start crawling.

A better network topology would be to use a SWITCH instead of a HUB as shown in the diagram below:

Really? A Switch?

DEFINITION TIME: A SWITCH is a multi-port device, which breaks the collision domain into the number of ports it has. It still has only 1 broadcast domain.

What the above definition means is that if the switch has 4 ports, it has 4 collision domains. That means 4 devices can communicate at the same time without collision. If any device sends a broadcast signal, every device connected to the switch WILL get that since it has only 1 broadcast domain!

But how does this configuration change anything from the previous configuration? Well for one, after Jack gets Jill's MAC address, Jack can start communicating exclusively with Jill, instead of his message being sent to all the devices connected to the switch! Like mentioned above, as the network grows with more devices, there will be so many collisions happening that the network will be literally JAMMED! A switch improves performance and also the bandwidth usage.

In addition to the differences mentioned above, one of the main differences between a hub and a switch is that a switch is an intelligent device. That means, as communication takes place, a switch will start learning MAC addresses of the devices connected to it and start storing it in its MAC ADDRESS TABLE. It also notes into which port a particular MAC address is connected. So the next time if any device wants to send a message to a particular MAC, the message will be automatically sent to that particular device!

Now let us assume that you have devices from different departments connected to this switch. So when any device sends a BROADCAST, all the devices receive these messages. Even if they know it is not meant for them, they will have to process a broadcast message! This is waste of precious device time and bandwidth. This problem will start magnifying as your network grows! So to break a large broadcast domains into smaller domains, we use a ROUTER. Lets have a look at the following diagram:

Please define a router.

DEFINITION TIME: A ROUTER is a device used to communicate to different networks. A router breaks the broadcast domain and collision domain, equal to the number of ports on it.

Suppose Jack and Jill are from HR and Tom and Sam are from Accounts, their devices need not send broadcast messages to each other. A router is a device used to communicate between networks/departments. They are also used to connect to the INTERNET.

The internet is made up of a lot of ROUTERs. These routers are so intelligent that they 'learn' about the routes to any network in the world. They use protocols to do this as you will learn in later chapters.

Alright, that will be all for the day!

Summary

We have learnt internetwork basics today. Let us summarize:

1. Definition and Types of Communication
2. Different network devices like HUB, SWITCH, ROUTER
3. Differences between these devices
4. Definition of Broadcast Domain and Collision Domain

Fastest Finger First

A) A HUB has ..........

1. Unlimited Broadcast and Collision Domain
2. 1 Broadcast and 1 Collision Domain
3. Collision Domain Equal to the number of ports and 1 Broadcast Domain
4. Broadcast Domain Equal to the number of ports and 1 Collision Domain

B) A SWITCH has ...........

1. Unlimited Broadcast and Collision Domain
2. 1 Broadcast and 1 Collision Domain
3. Collision Domain Equal to the number of ports and 1 Broadcast Domain
4. Broadcast Domain Equal to the number of ports and 1 Collision Domain

C) A Multicast means.........

1. One to many
2. One to All
3. One to One
4. Many to One

D) A Router is used for........

1. Connecting devices from the same network
2. Connecting devices from different network
3. Broadcast to all the port
4. All the above

Thank You!

If you have any queries, post it as a comment below. I will answer all your queries. Also as soon as you complete today's class, give the correct answers for FASTEST FINGER FIRST in the comment section below.

Chapter 1: Network Foundations

Note: I have discontinued this blog. Instead I have started a FREE video series on CCNA in YouTube. You can find it here. 

What is a Network?

In short, network is a collection of devices connected together that can communicate with each other! Here the key word is 'CONNECTED'. This connection is called a NETWORK.

If you notice in the image above, there are devices of different types, devices with different operating systems. Yet they all can communicate effortlessly over the network. This is the beauty of a computer network and what makes this so beautiful is what you will learn during the course of this training.

As an analogy, lets imagine how messages were sent in the olden days. A king writes a message and hands it to one of of his messenger. The messenger then rides a horse through the roads and delivers the message to the recipient. If we compare this to a computer network, the roads through which the messenger travelled represents the network! The message which the messenger carried are the network packets of information! That is the simplest explanation to describe a NETWORK!!!

Seems very interesting. Can you explain how it works?

For any device to connect with any other device, there needs to be a medium of connection. This medium is called a Network Interface Controller (NIC). The most common NIC available today is an ethernet card as given in the image below:

Another type of NIC is the Wireless card more commonly found on laptops, netbooks, tablets and mobile phones! Wired or wireless NIC has the same function - Connect the device to the NETWORK!

What are the types of Networks? Any ideas?

Well there are 5 major types of networks:

1. PAN (Personal Area Network)
2. LAN (Local Area Network)
3. WAN (Wide Area Network)
4. MAN (Metropolitan Area Network)
5. Internet (The mother of all networks!)

Personal Area Network (PAN):

A personal area network is a computer network revolving around an individual. It could as simple as a computer connected to a printer! This is the smallest chunk of a network!

NO STUPID QUESTION: What about a blue-tooth headset connected to your mobile phone? Yes, that is also a PAN!   

Local Area Network (LAN):

A local area network is a group of computers used in a local area, like an office or a department or a building. There is no limit to the number of computers in a LAN. The only thing defining a LAN is the size of the area, which needs to be geographically small, at most limiting it to a building.

Metropolitan Area Network (MAN):

A metropolitan area network is a group of computers extending to a single city.

Wide Area Network (WAN):

A wide area network is a group of computers spanning a wider area! It is a collection of two or more MANs.

Internet:

It is a collection of many WANs. It is the biggest network in the world, spanning the whole world!

Interesting, but you still did not tell us how it communicates!

Devices identify and communicate over the network using IP Addresses and respective protocols.

What is an IP Address?

1. An IP Address is a unique identifier for each device in a network
2. It is a 32bits binary number (example: 11010010 11100001 00010100 10101010)
3. The most popular way of representing this address is by Dotted Decimal form, which is separating every 8bit by a DOT(.) and converting each 8 bit to its decimal equivalent (example: 192.168.1.1)
4. Of the 32bits, some represent the network portion and other remaining the host portion (as explained later in the chapter)

Before we go any further, lets learn a bit about binary maths! A detailed explanation will be given in chapter: 'Day 5: Binary Maths'.

In the decimal number system (the one we use in everyday life) we have digits 0,1,2,3,4,5,6,7,8,9. They are a total of 10 digits and that is why it is called DECIMAL derived from the greek word 'δέκα', meaning TEN! Starting from 0 if we keep adding 1, it goes on till 9. After nine since we do not have a digit, we add 1 to the number on the left and reset the number to 0 and that is how we get 10! But BINARY has only 0 and 1, so if we keep increasing after 1, using the same rule add 1 to left and reset that digit to 0. As an example, lets see both the system:

DECIMAL                BINARY
0000                      0000
0001                      0001

0002                      0010

0003                      0011

0004                      0100

0005                      0101

0006                      0110

0007                      0111

0008                      1000

0009                      1001

0010                      1010

0011                      1011

0012                      1100

0013                      1101

So on so forth...

As explained above, an IP Addresses is a 32 bit binary number. Doing a bit of binary maths, we know with 32bits the biggest number is 4,294,967,296!!! (Got using the formulae: 2^[number of bits]). That means that you can have a maximum of 4,294,967,296 unique ip addresses. That is ip address going from:

00000000 00000000 00000000 00000000 (0.0.0.0)

00000000 00000000 00000000 00000001 (0.0.0.1)

00000000 00000000 00000000 00000010 (0.0.0.2)

00000000 00000000 00000000 00000011 (0.0.0.3)

00000000 00000000 00000000 00000100 (0.0.0.4)

00000000 00000000 00000000 00000101 (0.0.0.5)

00000000 00000000 00000000 00000110 (0.0.0.6)

00000000 00000000 00000000 00000111 (0.0.0.7)

00000000 00000000 00000000 00001000 (0.0.0.8)

TO

00000000 00000000 00000000 11111111 (0.0.0.255)

00000000 00000000 00000001 00000000 (0.0.1.0)

TO

00000000 00000000 00000001 11111111 (0.0.1.255)

00000000 00000000 00000010 00000000 (0.0.2.0)

TO

00000000 00000000 11111111 11111111 (0.0.255.255)

00000000 00000001 00000000 00000000 (0.1.255.255)

this will continue until all bits become '1'

11111111 11111111 11111111 11111111 (255.255.255.255)

But managing such a long list of ip address is a little tedious and impractical. For this reason ip addresses were broken down to classes. 

IP Address Classes

IP Addresses are grouped in classes depending on the first number in the Dotted Decimal as follows:

• If the number is between 0 - 127 : CLASS A
• If the number is between 128 - 191 : CLASS B
• If the number is between 192 - 223 : CLASS C
• If the number is between 224 - 239 : CLASS D (Reserved)
• If the number is between 240 - 255 : CLASS E (Reserved)

So the ip address: 192.168.1.1 is a CLASS C address, identified by the first number: 192!

Another one: 10.1.4.5 ? YES, CLASS A it is!!!

Okay one more: 172.16.1.1 ? Brilliant, it is indeed CLASS B!

IP Address Subnet Mask

If we look closely at any IP Address, they comprise of two parts!

NETWORK and HOST

It is like any email address: xyz@abc.com. So when you send an email, your email server first checks the domain you are sending the email to, which in this example is 'abc.com'. If your email server is also part of 'abc.com' then it knows it is a local email address and sends it to the relevant inbox. If it is on a different server than your email server, it send it out to its external gateway to be routed to the 'abc.com' domain. (NOTE: This is an overtly simplified process of how an email system works. This is just for explanation.)

Devices also communicate similarly as the above email example. If a packet (message) is sent from one computer to another, it first checks the NETWORK part of the ip address to see if it is in the same network. If it is, then it sends it to the local address. If it is not on the same network, it sends it out to the gateway to route it to the correct address.

But how does the device know which is the NETWORK and which is the host! That is where we make use of the SUBNET MASK. A network device compares the IP address along with the Subnet Mask, and identifies's the Network bits corresponding to the '1s' in the subnet mask and Host bits corresponding to the '0s' of the subnet mask. Lets look at an example. This is a CLASS C ip address and the CLASS C subnet mask is: 255.255.255.0

IP Address:    192.168.1.1     (11000000 10101000 00000001 00000001)

Subnet Mask: 255.255.255.0  (11111111 11111111 11111111 00000000)
----------------------------------------------------------------------------
If we AND the two together:  (11000000 10101000 00000001 00000000)

This will tell the device that '192.168.1' is the NETWORK and '.1' is the HOST. The host bits (the last 8 bits) can go from all '0s' to all '1s'! Doing a bit of binary maths, on the 8 bits available for HOSTs, we can have a maximum of 2^8=256 ip addresses! That is:

192.168.1.0 ---> Network IP
192.168.1.1
192.168.1.2
192.168.1.3
192.168.1.4
till
192.168.1.254
192.168.1.255 ---> Broadcast IP 

NOTE: Keep in mind that in any ip address, if all the HOST bits are '0s' it is the NETWORK address and if all the HOST bits are '1s' it is the BROADCAST address. These addresses cannot be used to assign any hosts. So the total number of VALID HOSTs in any network is got by the formulae: 2^(number of bits) - 2

Subnet Mask List for each Class:

Class A - 255.0.0.0 (24bits for HOST, that is 16,777,214 hosts)

Class B - 255.255.0.0 (16bits for HOST, that is 65,534 hosts)
Class C - 255.255.255.0 (8bits for HOST, that is 254 hosts)

As seen above, we have to decide on the best suited IP Address class to use for our network depending on the number of devices in our network. Using a class A ip addressing scheme for an office with only 4 devices would be wasting 16,777,210 ip addresses!!!

This is just a summary. Later in the course, when we do Subnetting, we will look into IP Address Classes in more detail. Use this chapter to understand the structure of an IP ADDRESS!

Summary

Alright that would be all for DAY 2! Let us summarize on what we learnt today!

1. Definition of a Network
2. How a network works
3. Types of Network
4. What is an IP Address
5. What are IP Address Classes
6. What is an IP Subnet Mask

Fastest Finger First

A) What is a NETWORK?

1. Devices connected together that can communicate with each other
2. Devices disconnected
3. Devices connected, but cannot communicate
4. None of the above

B) How many bits does an IP Address have?

1. 16
2. 8
3. 24
4. 32

C) What is a subnet mask?

1. A 32 bit number to identify a device
2. A 32 bit number to differentiate between Network and Host of an IP Address
3. A 32 bit number to identify a computer
4. A 4 digit decimal number

D) How many valid hosts can we have in a Class B IP Address?

1. 254
2. 65534
3. 16777214
4. 4294967296

Thank You!

If you have any queries, post it as a comment below. I will answer all your queries. Also as soon as you complete today's class, give the correct answers for FASTEST FINGER FIRST in the comment section below.

Introduction

Note: I have discontinued this blog. Instead I have started a FREE video series on CCNA in YouTube. You can find it here. 

What is CCNA?

CCNA is the acronym for Cisco Certified Network Associate, which I am sure you already know. But what makes CCNA the most sought after certification for people getting into the networking field? Well because it covers all the basics of networking and also gets you up to speed to start working and troubleshooting CISCO devices.

And why is that a big deal....?

Because CISCO is the largest networking device maker in the world and if you want to work in the networking field, you better be ready to deal with CISCO devices!

Ah... I see... then I need to know more about CCNA!

Well you have come to the right place for that! Let me take you through CISCO certifications process:

Cisco certification basically consists of 3 levels:

1. Associate
2. Professional
3. Expert

CCNA falls into the Associate level. You could become a CCNA in any of the domains offered like: Router & Switching, Security, Voice, Wireless, Service Provider, Service Provider Operations.

What skills do I need to become a CCNA?

To become a CCNA, you would need to aleast know the following:

1. Basics of OSI Model and TCP-IP Model
2. Binary and Decimal Maths
3. Basics of installing and configuring LAN, WAN and Wireless access services
4. Troubleshooting the above mentioned installations
5. Use protocols IP, IPv6, EIGRP, RIP, RIPv2 and OSPF
6. Understand Serial Connections, Frame Relay, VPN, cable, DSL, PPPoE, LAN Switching, VLANs, VTP, STP, Ethernet, Security and Access List

How do I become a CCNA?

To become a CCNA, you have multiple paths:

• Pass the CCNA composite exam with exam code: 640-802

OR

• Pass Interconnecting Cisco Networking Devices 1 (ICND1) and ICND2 with exam codes: 640-822 and 640-816

For exam cost and application procedures, go to this link.

Do not worry, if any of the above list makes you think it is hard! With CME®, we will make your journey to certification an easy one!

What is CME®?

CME® is an acronym for Certifications Made Easy. In today's world, a degree is not good enough if you aspire to climb the career ladder in the Information Technology world. Certifications keeps you up to date with latest technology and buys you that ladder to climb up in your careers.

CME® was founded to bridge the gap that existed in a reasonably priced quality training for the IT Industry. And you know what? We decided it should be FREE! Our aim is to make learning easy, fun and FREE, so that every body can benefit.

What is CME's differentiator from all available training materials online?

There are not too many quality training materials available online. Of the ones that are available, they are either not FREE or they are not very professional or BOTH.

CME®, like mentioned earlier, came into existence to bridge this gap. Training with CME® is like training with a friend. Our 'No Stupid Question' section in every chapter tries to ask all possible questions and gets them answered. Our training material language will be as a first person conversation, inspired from the HEAD FIRST series from O'Reilly Media. At the end of each chapter we will have a 'Fastest Finger First', multiple choice questions test relating to the chapter.

Who is the trainer for this series?

Glad you asked that, I thought you would forget! Well, my name is Imran Ahmed Rafai. I am an Electronics and Commucations Engineer from India. I also have a Masters in Business Administration specializing in Information Technology from Coventry University, United Kingdom. I am currently pursuing my CCIE (Voice), which I should be completing in another 3 months.

I think we have had enough of introduction. Let us get straight to our training!

What will be covered in this training and when?

Chapter 1: Network Foundations

Chapter 2: Inter-networking Basics

Chapter 3: Models 
Ethernet Network and Data Encapsulations

Binary Maths

Introduction to TCP/IP

Subnetting and VLSM

Cisco's IOS and SDM

Managing and Cisco Inter-network

IP Routing

EIGRP and OSPF

Layer 2 Switching

Virtual LAN

Security

NAT and PAT

IP v6

Wide Area Networking

Note: As I complete the entries, I will keep updating this list with the Day Number. Also I may tweak the list to cover every topic required for your CCNA! So keep checking back here!

How to use this training?

This training is like a classroom conversation between students and the trainer. I have marked conversations and sections as follows:

• A black text is a trainer conversation
• A green text is a student conversation
• A black background is a definition or something important to mark

All the very best and have a wonderful time going through this training!