I took 640-821, the first of the two that Cisco suggests you tackle, and received 50 questions in 90 minutes with a passing score of 867. Even though this was the beta version of this exam, a screen appeared prior to the test, which said, "This beta exam is in the late stages of development and a score report will be provided." I received a traditional score report, unlike any other beta I've ever taken.

	Exam #640-821: Introduction to Cisco Technologies (INTRO) Vendor Cisco Status Scheduled to go live shortly. Will be available at Pearson Vue and Prometric testing centers worldwide. Reviewer's Rating "This new exam will test your knowledge of basic router configuration, cable types, IOS commands, the OSI model and subnetting." Test Information 55 to 65 questions, 60 minute time limit. Cost: $100 (U.S.). Who Should Take This Exam? Candidates for CCNA; must take in conjuction with 640-811 ICND exam. Test Objectives Click here

I had three router simulators, many multiple choice questions and a few drag-and-drop items on my exam. Having taken the CCNA 407, 507, 607 and 801 exams, I found this exam much easier. It includes all my favorite topics; cable types, IOS commands, the OSI model and subnetting.

The exam engine is slow when it comes to switching between the simulator-based questions and the standard multiple choice questions. Patience is a must! For most simulator-based questions, you're presented with a router requirement and required to configure one or more routers and save and verify your work. The simulator behaves very much like the real thing and includes limited support for abbreviated, editing and help commands.

The main topics from the objectives list are: Design and Support, Implementation and Operation and Technology. Exam topics include: Network Types, Network Media, Switching Fundamentals, TCP/IP, IP Addressing and Routing, WAN Technologies, Operating and Configuring IOS Devices, and Managing Network Environments. In this article, I address many of these topics under their main headings to help you prepare for this exam.

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Design and Support
Under this general heading you'll find these topics: Use a subset of Cisco IOS commands to analyze and report network problems; use embedded layer 3 through layer 7 protocols to establish, test, suspend or disconnect connectivity to remote devices from the router console; and determine IP addresses.

Knowing the basic Cisco Internetworking Operating System commands has traditionally been up to one-third of the required knowledge for the aspiring CCNA. You should become conversant with the commands listed in Table 1.

Table 1. Basic IOS commands used to establish, test, suspend or disconnect connectivity to remote devices from the router console.

Tip: When interpreting the output of the ping command, exclamation points (!!!!!) represent echo replies and good connectivity.

Implementation and Operation
Under this general heading you'll find these topics listed: establish communication between a terminal device and the router IOS and use the IOS for system analysis; manipulate system image and device configuration files; perform an initial configuration on a router and save the resultant configuration file; use commands incorporated within the IOS to analyze and report network problems; assign IP addresses; describe and install the hardware and software required to be able to communicate via a network; and finally, use embedded data link functionality to perform network neighbor discovery and analysis from the router. Sounds like it's time for another table of commands!

To establish connectivity between a terminal device and the router's IOS, use an ASCII-compliant terminal-emulation program such as HyperTerminal or Telnet.

Type the console or VTY line password for user access or enable and the enable password for executive access.

See Table 2 below for IOS commands needed to manage connections, images and CDP.

Table 2. IOS commands for system analysis, manipulating system image and device configuration files, performing an initial configuration on a router and saving the resultant configuration file, use commands incorporated within IOS to analyze and report network problems and assigning IP addresses.

Tip: The boot system flash command configures the router's IOS to look for the IOS image in flash memory.

Technology
Under the final heading of Technology in the exam guide, you'll find a multitude of topics. Let me address them by providing my list of "things to know."

First, binary, hex and decimal are all numbering systems you should be intimately familiar with for this exam. Table 3 provides a conversion chart.

Table 3. Binary, hex and decimal conversions.

Computer network LAN topologies consist of bus, star and ring. In a bus and star network topology, data travels from end to end. In a ring topology, data travels in a ring. WAN topologies cover greater geographic distances and all data travels in a bit-by-bit serial fashion.

Tip: Data transmission flow control occurs with the help of buffering, windowing and congestion avoidance.

In token ring networks, a token is passed around the network from device to device. When a device has data to send, it must wait until it has the token before sending its data.

Tip: To connect a network device to any one of these network types, you need at a minimum a compatible network interface card and a connecting cable and protocol.

Network media includes wireless, twisted-pair and optical. Wireless uses no physical connectors. Twisted-pair is still the most common. UTP (Unshielded Twisted Pair) includes eight wires in four twisted pairs. Optical media includes fiber, which offers the greatest distance of the three types. Table 4, below, shows the most common of the twisted-pair wiring configurations.

Table 4. Common wiring configurations.

Tip: Routers are responsible for switching and routing of data packets.

Cisco routers include the following hardware and software components: CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), NVRAM (Non-Volatile RAM), IOS, mini-IOS and configuration files. A router startup process is like this:

1. Bootstrap loads from ROM.
2. Router finds IOS, usually from flash, and loads it.
3. Router finds and loads configuration file, usually from NVRAM.

Ethernet uses CSMA/CD for error detection and correction. It includes the following:

• Carrier sense. Each station continuously listens for traffic on the wire to determine when gaps between frames occur.
• Multiple accesses. Stations may begin transmitting any time they detect that the network is quiet.
• Collision detect. If two or more stations begin transmitting at the same time, the bits from the transmitting stations will collide with each other and both transmissions will be unreadable. If that happens, each transmitting station must be capable of detecting that a collision has occurred before it has finished sending its frame. Each must stop transmitting as soon as it has detected the collision and then must wait a random length of time (determined by a back-off algorithm) before attempting to retransmit the frame.

  Tip: Routers divide networks into different broadcast domains for controlling client and server network broadcast traffic. Switches and bridges create or divide collision domains.

How could any network student understand networking without knowing the OSI model? The OSI 7 layer reference model includes these layers, taking it from the top: Application, Presentation, Session, Transport, Network, Data Link, and Physical. The numbering starts from the bottom (physical layer is number 1). Knowing the layer names and their order is crucial. Some people like to use an anagram to help. One of my favorites (from the bottom up): Please Do Not Throw Sausage Pizza Away.

Knowing where the most common network devices operate in the OSI model is also a must. At the physical layer there is the cabling of the network, repeaters and hubs. The data link layer includes bridges and switches, and routers operate at the network layer.

Tip: A switch is really nothing more than a multi-port bridge.

Understanding protocol operation and at which layer each functions is an exam requirement. This exam focuses only on TCP/IP. From the physical layer up, there are protocols that define the physical connection and signaling on the wire such as V.35 and RS-232. At the data link layer there are also protocols responsible for defining the network topology and data communication standards such as ethernet, token-ring, and FDDI.

At the network layer, there's IP, ICMP, ARP. At the transport layer, there's TCP and UDP. UDP is fast and efficient but doesn't provide guaranteed delivery and retransmission like TCP. TCP is more commonly used at this layer by many upper-layer protocols and applications.

The Internet protocol suite includes many application-layer protocols that represent a wide variety of applications, including the following:

• FTP (File Transfer Protocol) -- moves files between devices.
• SNMP (Simple Network-Management Protocol) -- reports network conditions and sets network threshold values.
• Telnet -- serves as a terminal emulation protocol.
• SMTP (Simple Mail Transfer Protocol) -- provides electronic mail services.
• DNS (Domain Name System) -- translates the names of network nodes into network addresses.
• TFTP (Trivial File Transfer Protocol) -- allows for transfer of router files to and from a network workstation.

Table 5, below, lists the common application-layer protocols, their use of TCP or UDP and port number assignments.

Table 5. Common application-layer protocols, TCP or UDP, and port numbers.

Cisco requires you to know how to plan, assign, configure, subnet and troubleshoot IP addresses. A popular resource recommended by many for learning how to subnet is http://www.LearnToSubnet.com.

For this exam, you must have an understanding of the classes of IP addresses, their starting and ending ranges, default subnet masks, the minus-2 rule, how to figure and identify the first host, last host and broadcast address of any subnet, along with calculating the mask for a required number of networks or hosts or both.

Tip: Here's a technique to help calculate the subnet: 256 minus the subnet mask. For example; the address 192.168.0.22 255.255.255.240, is on the 192.168.0.16 subnet with subnets of 16, 32, 48, and so on. The first assignable address is 17, and the broadcast is 31.

That wraps it up for this exam review. If, after reading this review, you find you're not ready to prepare for the Cisco exams, consider Network+, the entry-level test put out by CompTIA. (You can find the objectives here.)

Cisco certification is a good way to gauge your understanding of networking and internetworking at the lower levels of the OSI reference model. It can also be the jumpstart you need to tackle other certifications, which are highly valued by employers and constantly push you to excel in your understanding of Cisco technologies and products. Good luck!

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