Subnetting?! You can do it!

Subnetting can be confusing until it is broken into steps and followed logically. Practicing these steps on a regular basis will enable one to understand subnetting.

Before attempting subnetting, one must understand how to work with binary and decimal number conversions. Let's review this first.

2⁰=1
2¹=2
2²=4
2³=8
2⁴=16
2⁵=32
2⁶=64
2⁷=128

The following pattern for solving binary numbers to decimal numbers and decimal numbers to binary numbers should be used. Always remember to read from right to left instead of left to right. Also notice that each place doubles in value from right to left.

27	26	25	24	23	22	21	20
128	64	32	16	8	4	2	1

The above should be memorized. Later this will be important to remember when figuring out the number of subnets and hosts per subnets. Therefore, this skill must be practiced and reinforced as often as possible. Here are a few sample problems.

Example 1 (binary to decimal)
11001011 = 203 or

27	26	25	24	23	22	21	20
128	64	32	16	8	4	2	1
1	1	0	0	1	0	1	1

Example 2 (binary to decimal)
01011110 = 94 or

27	26	25	24	23	22	21	20
128	64	32	16	8	4	2	1
0	1	0	1	1	1	1	0

By writing out the chart and placing the 1's and 0's under the proper place in the chart, all that is left is to add up the place values that have 1's under them and the total will be the decimal number value.

To convert decimal numbers to binary numbers, place 1's in the place values until all the place values with 1's add up to the total. If any numbered place adds a value that is larger than the decimal number, 0's should be placed in those place values.

Subnetting Review

When you are creating subnets,you must determine the optimal number of subnets and host.
To identify subnets, you will "borrow" bits from host ID portion of the IP address:

The number of subnets available depends on the number of bits borrowed.

• The available nmber of subnets =2s, I which s is the number of bits borrowed.

The number of hosts per subnet available depends upon yhe number of host ID bits not borrowed.

• The available number of hosts per subnet=2h-2, in which h is the number of host bits not borrowed.
• One address is reserved as the network address.
• One address is reserved as the broadcast address.
  

Resource-Sharing Functions and Benefits

This topic describes the major resource-sharing functions of a computer network and how each function beefits end users.

Network allow end users to share both information and hardware resources. The major resources that are shared in a computer network include the following:
• Data and application: When users are connected through a network, they can share files and even software application programs, making data more easily available and promoting more efficient collaboration on work projects.
• Resources: The resources that can be shared include both input devices, such as cameras, and output devices, such as printers.
• Network storage: Today there are several ways in which the network makes storage available to users. Direct attached storage (DAS) directly connects physical storage to a PC or a shared server. Network attached storage (NAS) makes storage available through a special network appliance. Finally, storage area network (SANs) provides a network of storage devices.
• Backup devices: A network can also include backup devices, such as tape drives, that provide a central means to save files from multiple computers. Network storage is also used to provide archive capability, business continuance, and disaster recovery.

The overall benefit to users who are connected by a network is an efficiency of operation through commonly available components that are used in everyday task-sharing files, printing, and storing data. This efficiency results in reduced expenditures and increased productivity.

In recent years, the openness that was once pervasive in networking has been replaced with a need for caution. There have been many well-advertised acts of “cyber vandalism” in which both end systems and network devices have been broken into; therefore, the need for network security has to be balanced with need for connectivity.

Common Physical Components of a Network

This topic describes the physical components of a network, including PCs, interconnections, switches, and routers.
These are the four major categories of physical components in a computer network:

• Personal computers (PCs): The computers serve as end points in the network, sending and receiving data.
• Interconnections: The interconnections consist of components that provide a means for data to travel from one point to another point in the network. This category includes components such as the following:

1. Network interface cards (NICs) that translate the data produced by the computer into a format that can be transmitted over the local network
2. Network media, such as cable or wireless media, that provide the means by which the signals are transmitted from one networked device to another
3. Connectors that provide the connection points for media

• Switches: Switches are device that provide network attachment to the end systems and intelligent switching of the data within the local network.
• Routers: Routers interconnect networks and choose the best paths between netwroks.
  

What is a Network?

A network is a connected collection of devices and end system, such as computers and servers, which can communicate with each other. Networks carry data in many types of environments, including homes, small businesses, and large enterprises. In a large enterprises, there may be a number of locations that need to communicate with each other, and you can describe those locations in terms of where the workers are located, as follows:

• Main office : A main office is a site where everyone is connected via a network and where the bulk of corporate information is located. A main office can have hundreds or even thousands of people who depend on network access to do their jobs. A main office may use several connected networks, which can span many floors in an office building or cover a campus that contains several buildings.

• Remote location : A variety of remote access locations use networks to connect to the main office or to each other.

1. Branch office : In branch offices, smaller groups of people work and communicate with each via a network. Although some corporate information may be stored at a branch office, it is more likely that branch offices have local network resources, such as printers, but must access information directly from the main office.
2. Home office : When individuals work from home, the location is called a home office. Home office workers often require on-demand connections to the main or branch offices to access information or use network resources such as file servers.
3. Mobile users : Mobile users connect to the main office network while at the main office, at the branch, or traveling. The network access needs of mobile users are based oh where the mobile users are located.

You may use a network in your home office to communicate via the Internet to locate information, place orders for merchandise, and send messages to friends. Or you may have a small office that it set up with a network that connect other computers and printers in the office. Or you may work in a large enterprise in which there are many computers, printers, storage devices, and servers that are used to communicate and store information from many departments over large geographic areas.

Cisco Certified Network Associate

CCNA is the acronym for the Cisco Certified Network Associate certification from Cisco. In speech and in writing, this certification is properly referred to by the initials CCNA rather than the full name.

CCNA certification is a second-level Cisco Career certification that indicates a foundation in apprentice knowledge of networking. CCNA certification validates the ability to install, configure, operate, and troubleshoot medium-size routed and switched networks, including implementation and verification of connections to remote sites in a WAN.

To become a CCNA, a passing score on the 640-802 exam must be achieved, or combined passing scores on both the ICND1 640-822 and ICND2 640-816 exams. Passing the ICND1 grants you the Cisco Certified Entry Networking Technician (CCENT). Passing scores are set by using statistical analysis and are subject to change. At the completion of the exam, candidates receive a score report along with a score breakout by exam section and the passing score for the given exam. Cisco does not publish exam passing scores because exam questions and passing scores are subject to change without notice.

Article Source : http://en.wikipedia.org/wiki/CCNA