CCNA (Cisco Certified Network Associate) Syllabus
2) OSI (Open System Interconnection) Reference Model
3) Network Devices
; Types of Communication
; LAN & WAN Concept
4) IP Addressing & Concepts
; Variable Length Subnet Scheme (VLSM)
; And Operation
6) IOS Boot up Sequence
; Dual (Booting)
7) IP Routing
; Static Route
; RIP (Routing Information Protocol)
; IGRP (Internet Gateway Routing Protocol)
; EIGRP (Enhance Internet Gateway Routing Protocol)
; OSPF (Open Shortest Path First)
; VLAN (Virtual Local Area Network)
; STP (Spanning Tree Protocol)
9) ACL (Access Control List)
10) WAN (Wide Area Network) Router as a Switch
11) Frame Relay
12) NAT & PAT Private & Public
13) WLAN (Wireless Local Area Network)
14) VOIP (Voice Over Internet Protocol)
CCNA (Cisco Certified Network Associate)
Cisco is company name, in course. Company may any, there are many companies i.e. Cisco, Motorola, Simons, Microsoft, but configurations are same. Cisco has 87% shares on infrastructure of IP. It is said that if you send any small information on Internet, this is impossible that this information do not pass through the Cisco Devices. Our purpose is not reading about any product or any company but only with technology.
Practically you know what you study.
This is a level in this line. Associate is the first level.
Our whole lab is around the one word i.e. “Network”.
“Connectivity of two or more than two devices so that you can communicate with each other, you can exchange the sources or share the information is called networking”. It has two parts:
Medium may any (copper, wire and wave) for the connectivity and communication. Connectivity is due to the Hardware and communication is due to the Software.
There is a telephone line connected to your home telephone set from PTCL exchange. Is this a network? No, because there is only connectivity but not communication. If an other person talks with you, it is communication. Here the both parts fulfil the definition. Now, you can say the “Network”.
Q: The signals from telephone exchange are analog signals. If you think that I have digital telephone set in home then why would these signals analog?
Ans: In old days when a number is dialed then the exchange had a mechanical arm. You can listen the sound of that arm as the sound of typewriter on every digits of your number. But there is no sound now a day, only this process is converted into digital. But the signals pass through media as analog.
Avoid Wrong Concept
If you use the modem in between the telephone exchange and your computer, then modem converts the analog signals into digital to analog signals, this concept is wrong.
The basic purpose of modem is modulation and demodulation.
Modulation & Demodulation
If you take a page and throw away with full capacity then this page (Information) will not travel more. But if you use a stone covered by paper (Information) then this paper will covered long distance with high speed. When this paper reached to other side, unwanted information (Stone) is removed to get information (Paper).
Insertion of carrier (Stone) into information for covering long distance is called “Modulation”. And distraction of carrier unwanted information is called “Demodulation”.
2) OSI (Open System Interconnection)
OSI Reference Model
The word reference always between two things, there is no reference of only a single thing. The eye‟s reference is with eye and the leg‟s reference with leg. This reference means there is any two devices is involved in this reference not one device. OSI Reference Model is not for a single machine, this model is for networks.
OSI stands for Open System Interconnection.
Q: Why is it said as Open System, why not as Close System?
Ans: As you know, “The connectivity of two or more than two devices so
that they can communicate which each other”.
there is not mentioned that medium would be copper, fiber, microwaves or radio waves for the connectivity. Media may be anything for the connectivity.
The other part of the definition “The connectivity of two or more than two devices”
devices mean it can be a router, switch, computer, modem or any other device.
Using your Internet, when you send an email or chat with other by MSN Messenger, there is not a condition that those only those people can send emails or chat with each other that had the same machines both sides. Machines may be of any vendor i.e. IBM, Compaq or Dell.
You can use any media, any vender‟s computer and any operating system for connectivity and sharing resources. So it is known as Open i.e. open for every one.
If the OSI System was as Close System then it means, Internet will use the people that have only Compaq machines.
OSI Model is a Layered Approach (Structured Approach), which is made to understand the Internet or network.
Layered Approach OR Structured Approach
If you understand the human, then you can say this is a human being, which is divided into structure. Like head, eyes, nose, hand mouth etc. Each part of body has its own function.
Q: What is advantage of Layered Approach?
If there is one person is working in a company, that person is marketing manager, technical manager, receptionist and peon also. This single person is responsible for all working of company.
After one year, there is a visit of Chief Executive by chance, he asked that person about the dirtiness of office. He replied that I have been involving in technical matter, marketing all day so I have not time. The employee accepts the responsibility of office but he presents logic also. In this situation you cannot blame on the employee.
On the other hand if there is division like: there are separate employees on all departments i.e. marketing, technical, receptionist and peon.
When Chief Executive came and asked the peon about the dirtiness of office. This is an error by the peon not marketing or technical manager. Company has no business in this whole year this error is by the marketing manager not peon or receptionist or any other person.
By using Layered Approach you can find out the errors on accurate location. If there is not layered approach then there is very difficult to find out the errors and also resolving these errors.
Using Internet, when you dial to connect to the Internet, messages may show like” There is no dial tone”, “Invalid User Name / Pass Word”. If you see the word only as
“Error” then you cannot find out the exact location of error. After seeing messages you will check the appropriate location for resolving the error.
Remember the word HELLO is not for our machine but it is another machine.
Example (Physical Session)
If you want to go to Lahore from Islamabad, then there are two ways. First is that you reached at Lahore without informing that person. When you asked about that person, you find that person is not available. You will come back by spending patrol, time without any progress.
Example (Virtual Session)
If you call that person before go to Lahore, if that person is available then I will move, otherwise I will not move. The advantage of this virtual session was, you have saved their resources.
Virtual Session provides the information about the other party available or not and also saving the resources.
This layer normally to be said as G.M. This G.M. wants to move another G.M. of Company for meeting. There are seven gates for going, but only one gate from which G.M can go out. When two computers connected with each other then this is physical layer.
Using MSN Messenger, you want to chat another person, if that person is available then the other window is opened otherwise a message will display as “User is not available”
4. Transport Layer
If other machine is available then this layer is responsible to transport the data on network. For the transport of data fragmentation is made. “The conversion of data into small pieces is called fragmentation or permutation”. E.g. HELLO is converted as:
H E L L O
3. Network Layer
Its major function is sorting and distribution. For understanding you consider this layer as a “Post Office” and Router as “Post Box”. On this layer a device is used called as “Router”. The pieces of HELLO are sent to a device called Router, which acts as sorting and distribution. In Post Office there is sorting is done, like all mails of Islamabad, Lahore etc. is separated for the distribution to their destinations.
In old days when you send a letter to any one, which is called mail. There are two possibilities, the mail reached at exact location or do not reach.
2. Data Link Layer
Logical Link Control
LLC Sub Layer LLC Sub Layer
Data Link Data Link
Physical MAC Sub Layer
Media Access Control
There are two sub layers.
1) LLC(Logical Link Control)
LLC layer finish hardware and software dependsies.
If we use “Pentium 1” computer and “Windows 98” one side and “Pentium 4”
computer and “Windows XP” other side then data speed and operating system clash between two computer but that layer finish that problem
2) MAC(Media Access Control)
There is MAC address exist, MAC address have used many devices like switches and LAN card.
As you know that data travel in form of 0 & 1 (these are the voltage level not mathematical and other number ), every device may contain different voltage, its means there is the involvement of voltage. If you have 3 or 5 voltage and its parallel there is line of any high voltage, then it may harm your data.
During watching TV, you some time see lining on your TV set, this is why with any high voltage.
Same like above, if there is any data cable contains 3 volts but its parallel a high 5 volts is passing then it is very possible that any bit of your data changes (i.e. 0 to 1).
During the chatting on messenger a person asked what is your age, he writes answer 25 and sends. During the data traveling its only one bit changes and your information will be changed as 65.
In reality no any system is so week, so to resolve this problem a layer is introduced called Data Link Layer. Its main function is the deduction of error.
CRC: (Cyclic Redundancy Code)
This algorithm is very important and famous. There may were mistakes take place, so an error deduction algorithm is made. It attaches an algorithm for sending data to the other side as it is.
If we have data 25 (5 5) and generators of link side are 5. That generator will divide the 5 / 5 and remainder will 0. When you send 25 on Internet then not only 25 is passing but the footers (tailors) also. Due to some error the word 26 (5 5 1) instead of 25 is changed, on the other machine there will be attached a CRC Algorithm again to check the both checksum. If there is any different then there is any error in that data which you sent. If there is an error then your system (Receiver) will not correct that error but it will say to the sender to correct.
Retransmission is faster as compared to error correction.
There are two sources for errors:
a) Errors within the Machine or System (i.e. Computers, Routers, Modems etc)
b) Errors from outside the Machine (i.e. in media when data is sent)
According to the research there is 99% probability of error when data travels on Media. The error in system is very rare, if may occur then system recover or restore from its own cache.
1. Physical Layer:
After all the layers exist on a cable is attached to your computer, this cable works on which level is called physical layer.
If you make a file and give to a peon for send to another place. The peon will move physically for the delivery of that file. The work of peon is to carry the data as it is.
Above you sent the word HELLO to other machine, this word travels on all layers by sequence, but if there is an error between the layers then the chances of data to be corrupted.
Q: Where that corrupted data is checked?
Ans: There is another Data Link Layer to the other side of Computer. From sender, the algorithm is attached with the data and will re verify by other side.
Switch, NIC Card (LAN Card) work on Data Link Layer.
Presentation PDU Session Upper-Layer Data
Transport Segment TCP Header Upper-Layer Data
Network Packet IP Header Data
LLC Header Data FCS Data-Link Frame
MAC Header Data FCS
Physical Bits 0101110101001000010
There are all opposite works are done to other side of machine.
Protocol is a same set of rules and regulations for the communication between two different machines on the same layer level.
Company “A” Company “B”
1. G.M (Application) G.M (Application)
2. Secretary (Session) Secretary (Session)
3. Peon (Physical) Peon (Physical)
According to rules, is there possible that the G.M of Company “A” call to the Peon of Company “B” everyday?
By above definition of Protocols, the relation of these companies will as under:
The main function of Protocols is the communication.
By the definition of Network:
The connectivity is due to the hardware and the communication is because of the software.
Protocols are software. On the Internet or network no any work is done without protocols. If there is no protocol then there is no any communication.