Proving your expertise in internetworking doesn't have to be hard. Cisco's latest exam
combination will let you obtain your CCNA credential in two steps.
A new path to Cisco Systems' CCNA, 640-821 allows you to achieve certification in two
small steps instead of one giant leap. You can now choose which path to take in obtaining
your CCNA. You can pass a single exam, 640-801. Or you can tackle two tests: 640-811,
the new ICND (Interconnecting Cisco Networking Devices) exam and 640-821, INTRO.
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.
I had three router simulators, many
multiple choice questions and a few dragand-
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.
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.
Remember your OSI layer assignments for this exam. Ping and tracert are Network
layer (3) commands; telnet operates at the Application layer (7).
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 ASCIIcompliant
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:
Bootstrap loads from ROM.
Router finds IOS, usually from flash, and
loads it.
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.
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.
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.
