Troy’s checklist for preparing for the CCNA: Objective 1

May 28, 2009 at 2:28 pm | Posted in Cisco | 2 Comments
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If you are reading this, chances are you have committed yourself (or are considering committing yourself) to achieving the coveted Cisco Certified Network Associate certification. If you have made the commitment, congratulations! If you are still watching with hesitation from the sidelines, come on and get in the game!

Welcome to my personal checklist to preparing for the CCNA exam. When I was a trainer, these are the topics I really emphasized for my students pre-exam. There are a ton of potential concepts you could be tested on, and it is extremely helpful to know where to focus your efforts. In my previous post here, I took a broad look at the objectives. In my next posts, I’ll break each section of the objectives down and discuss where your focus should be in each section.

The CCNA objectives are posted on the Cisco website here: I will use them as a framework to discuss the topics where you should focus your attention. Do not attempt the test without knowing the following items.

Objective 1: Describe how a network works

You should know the function of each type of network device, including routers, switches hubs and CSU/DSUs. You should know the following for each device:

  • The layer of the OSI model on which it operates.
  • The role the  device plays in the network.
  • The situation in which a particular device is required.

As a corrollary, you should be able to identify each device in a network diagram. Cisco uses specific icons for routers, switches, and hubs, and you must be able to recognize a device by its icon. They may not be labeled with their function on the test.

You should have the OSI model down cold. You should know:

  • The name and the number of each layer and its function.
  • What protocols and devices map to each layer (for example, a switch maps to the data link layer or Layer 2; TCP maps to the transport layer or Layer 4).
  • How data encapsulation works in conjunction with the OSI model.
  • What type of information each layer adds to the packet as it is being formed (packet formation IS encapsulation).

You should know the ports numbers of common network applications, such as:

  • FTP – 21
  • DNS – 53
  • Telnet – 23
  • HTTP – 80

(This is not all of them. Your textbook should have a list of about 10 to 15 port numbers that you should have memorized.)

You should be able to view a network diagram and understand what you are seeing. You should be able to translate to and from dotted decimal and binary numeric formats.

  • Since CIDR notation will be use instead of dotted decimal format for subnet masks, you should know what /22 means (255.255.252).
  • You should be able to view the IP addresses used and spot an IP addressing problems, such as an incorrect gateway or an IP address that is not in the subnet.
  • You must understand subnetting backwards and forwards. For example, if I gave you the addresses and and I ask you if they are in the same subnet, would you know? (Answer: They are NOT.)

You should understand when IP addresses are used for communication and when MAC addresses are used. (IP addresses are used for routing, but the communication within a subnet is done by way of MAC addresses.) Understand how this works and the role that ARP plays in the process.

You should understand the differences between LAN communication and WAN communication. You be familiar with:

  • The protocols used for WANS and LANS (they are different).
  • How LAN protocols and WAN protocols work together. (The original LAN packet is wrapped or encapsulated in the WAN protocol for delivery. Then the LAN packet emerges on the far end of the WAN link unencapsulated.)

You should be able to troubleshoot a network problem by using a layered approach, such as:

  • A cabling problem is a physical layer or Layer 1 problem.
  • An IP address problem is a network layer or Layer 3 problem.
  • An incorrect DLCI on a WAN link is a data link layer or Layer 2 problem.

Stay tuned for my coverage of Objective 2 next week!


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  1. FYI.. you have your FTP and telnet ports switched…

    • AAHHH. Not anymore; thanks for the fix. I blame the blog editor… that’s it!

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