Half and Full Duplex Ethernet

Half-duplex Ethernet is defined in the original 802.3 Ehternet; cisco says it uses only one wire pair with a digital signal running in both direction on the wire.

Half-duplex Ethernet-typically 10 BaseT- is only about 30 to 40 percent efficient as cisco sees it because a large 10 Base T network will usually only give you 3 to 4 Mbps at most.

Full Duplex Ehternet is supposed to offer 100 percent efficiency in both directions.

Full-duplex Ethernet can be used in three situtions:-

• With a connection from a switch to a host.

• With a connection from a switch to a switch.

• With a connection from a host to a host using a crossover cable.

Ethernet Networking

Ethernet is a connection media access method that allows all hosts on a network to share the same bandwith of a link. Ethernet networking uses carrier sense multiple access with collision detection(CSMA/CD) a protocol that helps devices share the bandwith evenly without having two devices transmit at the same time on the network medium.

The OSI Reference Model

One of the greatest functions of the OSI(Open Systems Interconnection) Specifications is to assist in data transfer between disparent hosts.

The OSI isnt't a physical model, though. Rather, its a set of guidlines that application developers can use to creat and implement application that run on a network.

The OSI have seven different layers, divided into two groups. The top three layers define how the application within the end stations will communicate with each other and with users.

The bottom four layers define how data is transmitted end to end.

The upper layers:-

• Application:- Provides a user interface.

• Presentation:- Present data, Handles processing such as encryption.

• Session:- Keeps different application data separate.

The lower layers:-

• Transport:- Provides reliable or unreliable delivery, performs error correction before retransmit.

• Network:- Provides logical addressing which routers use for path determination.

• Data Link:- Combines packets into bytes and bytes into frames, performs error detection not correction.

• Physical:- Moves bits between devices, Specifies voltage,wire speed.
  

Internetworking Basics

Networks and networking have grown exponentially over the last 15 years. They've had to evolve at light speed just to keep up with huge increase in basic mission critical users needs such as sharing data and printers as well as more advanced demands such as videoconferencing.
You can get a picture of a basic LAN network that's connected together using a hub. This network is actually one collision domain and one broadcast domain.

How Do You Become a CCNA?

The way to become a CCNA is to pass one little test(CCNA composite exam 640-802). Then-proof- you are a CCNA.(Dont you wish it were that easy?)

However, Cisco has a two-step process that you can take in order to become a CCNA that may or may not be easier than taking one longer exam.

The two-step method involves passing the following:

• Exam 640-822: Interconnecting Cisco Networking Devices 1 (ICND 1)

• Exam 640-816: Introduction to Cisco Networking Devices 2 (ICND 2)

What Skills Do You Need to Become a CCNA ?

To meet the CCNA certification skill level, you must be able to understand or do the following:

• A CCNA certified professional can install, configure, and operate LAN,WAN, and wireless access services securely, as well as troubleshoot and cinfigure small to medium networks for performance.

• This knowledge includes, but is not limited to, use of these protocols: IP, IPv6, EIGRP, RIP,RIPv2,OSPF,serial connections, Frame Relay, cable,DSL,PPPoE,LAN switching, VLANs, Ethernet, security, and access lists.
  

Why Become a CCNA ?

Cisco, not unlike Microsoft and Novell (Linux), has created the certification process to give administrations a set of skills and to equip prospective employers with a way to measure skills or match certain criteria.

The CCNA program was created to provide a solid introduction not only to the Cisco internetwork Oparating system(IOS) and Cisco hardware, but also to internetwork in general, making helpful to you in areas that are not exclusively Cisco's.

Cisco Certified Network Associate(CCNA)

The CCNA certification was the first in the new line of Cisco certification and was the pre-cursor to all current Cisco certification. Now you can become a Cisco Certified Network Associate for the coast of one test $150 & two test $125 each although the CCNA exams are extremely hard and cover a lot of material, so you have to really know your stuff.

Cisco is the king of routing,switching,and security, the microsoft of the internetworking world.The Cisco certifications reach beyond the popular certifications, such as the MCSE, to provide you with an indispensable factor in understanding todays network-insight into the Cisco world of internetworking. By deciding that you want to become Cisco certified.