Before we continue on with part 4 I thought I’d show you a different approach to subnetting. Subnetting as you know can be a difficult concept to master, hope this helps.

IP Addressing part 3 covers Host addressing and Subnetting. I love this guys accent, I like the way he pronounces router. Part 4 in this series continues on with more subnetting but before I post part 4, I’m going to post another video on subnetting. Subnetting can be a difficult subject for some and I thought a different style of teaching might be helpful.

If you like this video, please click on the tweet icon in the upper right and re-tweet this post. Thanks! Now on with the movie.

IP Addressing Part 2 of 5 – How do computers tell the difference between a Class A, Class B, Etc… IP address.

Here is part 2 of CCNA IP Addressing.

I’ve been distracted lately with a prelaunch, Internet marketing and cash gifting is a current interest of mine.  So, until I can get back into the book, I thought I’d post some video’s.
This first video is on IP addressing and it a series of 5 videos.

IP Addressing 1 of 5

If you find this video useful “Please” hit the tweet button and re-tweet. Thanks!

The following are chapter 3 test questions on Fundamentals of LAN’s. If you can answer 11 out of 11 or 10 out of 11 , you may want to just skim this chapter and jump to chapter 4.

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Fundamentals of LAN’s

1. Which of the following is true about the cabling of a typical modern Ethernet LAN?

a. Connect each device in series using coaxial cabling
b. Connect each device in series using UTP cabling
c. Connect each device to a centralized LAN hub using UTP cabling
d. Connect each device to a centralized LAN switch using UTP cabling

2. Which of the following is true about the cabling of a 10BASE2 Ethernet LAN?

a. Connect each device in series using coaxial cabling
b. Connect each device in series using UTP cabling
c. Connect each device to a centralized LAN hub using UTP cabling
d. Connect each device to a centralized LAN switch using UTP cabling

3. Which of the following is true about Ethernet crossover cables?

a. Pins 1 and 2 are reversed on the other end of the cable.
b. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of the cable.
c. Pins 1 and 2 on one end of the cable connect to pins 3 and 4 on the other end of the cable.
d. The cable can be up to 1000 meters long to cross over between buildings.
e. None of the other answers is correct.

4. Each answer lists two types of devices used in a 100BASE-TX network. If these devices were connected with UTP Ethernet cables, which pairs of devices would require a straight-through cable?

a. PC and router
b. PC and switch
c. Hub and switch
d. Router and hub
e. Wireless access point (Ethernet port) and switch

5. Which of the following is true about the CSMA/CD algorithm?

a. The algorithm never allows collisions to occur.
b. Collisions can happen, but the algorithm defines how the computers should notice a collision and how to recover.
c. The algorithm works with only two devices on the same Ethernet.
d. None of the other answers is correct.

6. Which of the following is a collision domain?

a. All devices connected to an Ethernet hub
b. All devices connected to an Ethernet switch
c. Two PCs, with one cabled to a router Ethernet port with a crossover cable and the other PC cabled to another router Ethernet port with a crossover cable
d. None of the other answers is correct.

7. Which of the following describe a shortcoming of using hubs that is improved by instead using switches?

a. Hubs create a single electrical bus to which all devices connect, causing the
devices to share the bandwidth.
b. Hubs limit the maximum cable length of individual cables (relative to switches)
c. Hubs allow collisions to occur when two attached devices send data at the same time.
d. Hubs restrict the number of physical ports to at most eight.

8. Which of the following terms describe Ethernet addresses that can be used to communicate with more than one device at a time?

a. Burned-in address
b. Unicast address
c. Broadcast address
d. Multicast address

9. Which of the following is one of the functions of OSI Layer 2 protocols?

a. Framing
b. Delivery of bits from one device to another
c. Error recovery
d. Defining the size and shape of Ethernet cards

10. Which of the following are true about the format of Ethernet addresses?

a. Each manufacturer puts a unique code into the first 2 bytes of the address.
b. Each manufacturer puts a unique code into the first 3 bytes of the address.
c. Each manufacturer puts a unique code into the first half of the address.
d. The part of the address that holds this manufacturer’s code is called the MAC.
e. The part of the address that holds this manufacturer’s code is called the OUI.
f. The part of the address that holds this manufacturer’s code has no specific name.

11. Which of the following is true about the Ethernet FCS field?

a. It is used for error recovery.
b. It is 2 bytes long.
c. It resides in the Ethernet trailer, not the Ethernet header.
d. It is used for encryption.
e. None of the other answers is correct.

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The OSI Reference Model

To pass the ICND1 exam, you must be conversant in a protocol specification with which you are very unlikely to ever have any hands-on experience—the OSI reference model. The difficulty these days when discussing the OSI protocol specifications is that you have no point of reference, because most people cannot simply walk down the hall and use a computer whose main, or even optional, networking protocols conform to the entire OSI model.

OSI is the Open System Interconnection reference model for communications.

OSI Layers and Their Functions

Cisco requires that CCNAs demonstrate a basic understanding of the functions defined by each OSI layer, as well as remembering the names of the layers. It is also important that, for each device or protocol referenced throughout the book, you understand which layers of the OSI model most closely match the functions defined by that device or protocol. The
upper layers of the OSI reference model (application, presentation, and session—Layers 7, 6, and 5) define functions focused on the application. The lower four layers (transport, network, data link, and physical—Layers 4, 3, 2, and 1) define functions focused on endto-end delivery of the data. The CCNA exams focus on issues in the lower layers—in particular, with Layer 2, upon which LAN switching is based, and Layer 3, upon which routing is based. Table 2-4 defines the functions of the seven layers.

Note: You need to memorize the table above. Here are a few mnemonic phrases to help you:

* All People Seem To Need Data Processing (Layers 7 to 1)
* Please Do Not Take Sausage Pizzas Away (Layers 1 to 7)
* Pew! Dead Ninja Turtles Smell Particularly Awful (Layers 1 to 7)

Next up: Chapter 3 Fundamentals of LANs

The network access layer defines the protocols and hardware required to deliver data across some physical network. The term network access refers to the fact that this layer defines how to physically connect a host computer to the physical media over which data can be transmitted. For instance, Ethernet is one example protocol at the TCP/IP network access layer. Ethernet defines the required cabling, addressing, and protocols used to create an Ethernet LAN. Likewise, the connectors, cables, voltage levels, and protocols used to
deliver data across WAN links are defined in a variety of other protocols that also fall into the network access layer.

The network access layer includes a large number of protocols. For instance, the network access layer includes all the variations of Ethernet protocols and other LAN standards. This layer also includes the popular WAN standards, such as the Point-to-Point Protocol (PPP) and Frame Relay.

In short, the TCP/IP network access layer includes the protocols, cabling standards, headers, and trailers that define how to send data across a wide variety of types of physical networks.

CAUTION: Many people describe the network access layer of the TCP/IP model as two layers, the data link layer and the physical layer. The reasons for the popularity of these alternate terms are explained in the section covering OSI, because the terms originated with the OSI model.

Next up:The OSI Reference Model

The internet layer of the TCP/IP networking model, primarily defined by the Internet Protocol (IP), works much like the postal service. IP defines addresses so that each host computer can have a different IP address, just as the postal service defines addressing that allows unique addresses for each house, apartment, and business. Similarly, IP defines the process of routing so that devices called routers can choose where to send packets of data so that they are delivered to the correct destination.

IP defines logical addresses, called IP addresses, which allow each TCP/IP-speaking device (called IP hosts) to have an address with which to communicate. IP also defines routing, the process of how a router should forward, or route, packets of data.

All the CCNA exams cover IP fairly deeply. For the ICND1 exam, this book’s Chapter 5 covers more of the basics, with Chapters 11 through 15 covering IP in much more detail.

Next up is the Network Access Layer…

The TCP/IP transport layer consists of two main protocol options:
the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

TCP/IP needs a mechanism to guarantee delivery of data across a network and the transport layer handles this. In short the transport layer provides a service to the layer above it, the application layer.

The benefits of TCP error recovery cannot be seen unless the data is lost. Let’s say Bob’s web browser was to request information from Larry’s server,  if either transmission were lost (Bob’s request to Larry or Larry’s response to Bob), HTTP would not take any direct action, but TCP would resend the data and ensure that it was received successfully.

In the above example demonstrates a function called adjacent-layer interaction, which defines the concepts of how adjacent layers in a networking model, on the same computer, work together. The
higher-layer protocol (HTTP) needs to do something it cannot do (error recovery). So, the higher layer asks for the next lower-layer protocol (TCP) to perform the service, and the next lower layer performs the service. The lower layer provides a service to the layer above it.

TCP/IP defines a large collection of protocols that allow computers to communicate.

What is discussed in chapter 2 is very general in nature and will be gone into depth in later chapters.

TCP/IP defines the details of each of these protocols inside documents called Requests for Comments (RFC).

The TCP/IP model represented in column 1 of the table lists the four layers of TCP/IP, and column 2 of the table lists several of the most popular TCP/IP protocols.

The TCP/IP Application Layer

The application layer provides an interface between software running on a
computer and the network itself. The application layer does not define the application itself, but rather it defines services that applications need—such as the capability to transfer a file in the case of HTTP.

Important general concepts behind networking models: when a particular layer on one computer wants to communicate with the same layer on another computer, the two computers use headers to hold the information that they want to communicate. The headers are part of what is transmitted between the two computers. This process is called same-layer interaction.