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My version of the exam gave me 50 questions to complete in 75 minutes. The passing score was 849. The test included two router simulations to configure as well as many multiple-choice questions for which I had to designate one or many correct answers as specified. Since I've taken both the 407 and 507 versions of the CCNA exam, I can tell that the 607 isn't much different. You'll find the official exam objectives listed on the Cisco certification Web site here.

The exam includes a router simulator and an entirely new exam interface and engine. The engine is slow when it comes to switching between the router simulator questions and the multiple-choice questions. In the simulation questions, you're presented with a fictitious company's network scenario and diagram and asked to perform router command line configurations to set up and reconfigure the network as necessary to create an operational network.

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The simulator behaves very much like a real router. It supports abbreviated commands, and when you've configured everything correctly, the interface shows states of up and up. One crucial difference to note: Help commands such as ? don't work -- for obvious reasons. In addition, you'll come across fill-in-the-blank questions, but they provide enough detail that you won't have to recall the answers from memory.

Bridging and Switching
Every CCNA should understand what happens within a Cisco switch and the bridging functions of a network at the OSI Data Link layer. Become knowledgeable about Spanning Tree Protocol (STP) and Virtual LANs and the two switching methods, Cut-through and Store-and-Forward. Cut-through switching is a preferred method when media collisions are low and latency at the switch can't be tolerated. Store-and-Forward, on the other hand, is needed when media collisions are high and a fixed latency is required.

Cisco switches enable STP by default. This, along with the Spanning Tree Algorithm (STA), enables switches to avoid network loops and minimize broadcast storms. STP allows the switches to exchange Bridge Protocol Data Units for choosing a Root bridge (a switch in this case) and determining where the network loops are present. Then the STA requires that switches responsible for creating loops place their redundant port or ports in a blocked state to prevent network loops.

VLANs have become a popular implementation method to connect network clients and their preferred servers logically, through the switched networks, without having to connect them to the same physical switch. VLANs are generally configured within the switches by the network administrator. They can offer levels of security and control, plus limit network broadcast traffic much like routers.

Bridges and switches perform the same function by dividing the network into different collision domains and forwarding traffic based upon MAC addresses. Routers, on the other hand, divide networks into different broadcast domains for controlling client and server network broadcast traffic.

Tip: Remember that you can divide your broadcast domains with switches at the Data Link layer (explained shortly) by using VLANs.

The OSI Reference Model
How could any network guru get through an average day's challenges and configurations without knowing the OSI seven-layer reference model? There's so much to learn in this area that it often overwhelms the new networking student. Just when you think you have a grasp on the layers and their basic functions, you learn there are many different protocols that reside at each layer depending on your network's primary protocol of communication.

The OSI model includes these layers, from the top: Application, Presentation, Session, Transport, Network, Data Link, and Physical. The numbering starts from the bottom (Physical layer is layer number 1). Remember the layer names. Some people like to use an anagram to help. One of my favorites is: "Please Do Not Throw Sausage Pizza Away."

Why does the OSI reference model exist and why is it so important? Many vendors are responsible for creating networking devices, software and protocols. The OSI model allows them to create products with interoperability and consistency. It also allows them to focus their development within the layer of responsibility. Router manufactures are concerned with routing, which operates at layer 3, the Network layer.

You also need to consider protocols and the layer at which they operate. From the Physical layer up, protocols define the physical connection and signaling on the wire, such as V.35, RS-232, Ethernet, Token Ring and FDDI.

For the sake of this discussion, I'll focus on the TCP/IP protocol, since it has become the protocol of choice in most networks. (Of course, there's also the TCP/IP four-layer reference model, which, from the top, includes the Application, Transport, Internet and Network layers.)

Let's address the OSI layers one at a time:

• Physical Layer --- This is where repeaters and hubs reside. Also defined at this layer are cabling types and connectors such as 100BaseTX, 10Base2, RJ-45 and BNC. Tip: The 100 and 10 in 100BaseTX or 10Base2 relate to the maximum speed for data transmission. The Base defines the signaling method. In this case it's representative of a single signal. The last part represents the actual cable type, whether twisted pair or coaxial, and the maximum length of a cable segment. Twisted pair generally supports lengths of 100 meters and thinnet coaxial supports a maximum distance of 185 meters.
• Data Link Layer -- Includes bridges and switches. Protocols at this layer are responsible for defining the network topology and data communication standards, such as Ethernet or 802.3, Token-Ring or 802.5, and FDDI.
• Network Layer - Staying with our primary protocol TCP/IP, this is where you'll find IP, which is defined as a routed network protocol. This is also where routing protocols RIP and IGRP reside. Then there is ARP, which IP uses to map its addresses to the addresses found at layer 2, such as MAC addresses for LAN network connections.
• Transport Layer - Home of TCP and UDP. TCP is more commonly used at this layer by many of the upper-layer protocols and applications. UDP is fast and efficient, but doesn't provide guaranteed delivery or retransmission like TCP does.
• Session Layer -- This layer is responsible for the session control between network stations. Here you'll find DNS and NetBIOS over TCP/IP.
• Presentation Layer -- Holds formatting and conversion protocols like MP3, TIFF and JPEG.
• Application Layer -- Contains Telnet, FTP, TFTP, SMTP and many other application-type protocols.

  Tip: Make sure you understand the conversion steps of data encapsulation. At the Physical layer bits are defined, and at the Data Link layer bits become frames. Frames become packets at the Network layer and those become segments at the Transport layer. For layers five through seven the data is referred to as datagrams or application data.

Network Protocols
Cisco requires you to know how to assign, configure, subnet and troubleshoot IP and IPX addresses. This means you must have a thorough understanding of IP addressing and subnetting. Know the three classes of IP addresses, A, B and C, and their starting and ending boundaries. Make sure you understand default subnet masks and subnetting rules such as the minus-2 rule. For instance, how many subnets can be created with a class C network address when allowing for at least 60 host IDs per subnetted network?

Tip: If you want to learn more about subnetting, visit LearnToSubnet.com.

IP relies upon the error reporting protocol ICMP. When you ping a device to verify connectivity at layer three, ICMP is responsible for the echo replies. In most cases you ping an individual host IP address and not the network's broadcast address.

Cisco also expects you to understand the IPX address format with network ID and host ID.

Tip: An IPX address is actually the station's MAC address preceded by the assigned IPX network number. You can easily recognize it, since it's written in the hexadecimal numbering format.

Routing
Routing is one of the main reasons for Cisco's existence. Your configuration of routers enables them to discover (via routing protocols) the path to use within a network. Connected and static routes are usually preferred, since they have some of the lowest administrative distances.

When viewing the routing table of a Cisco router, you'll see two values in brackets, for example [100/2]. This indicates the administrative distance and hop count (or other metric). Also indicated next to each route in the table is whether it's a connected route, C, or static route, S, or has possibly learned dynamically via a routing protocol with designations such as R for RIP and I for IGRP. The routing protocols RIP and IGRP are distance-vector routing protocols. They use metrics for path determination such as hop count for RIP and a combination of bandwidth and delay as in the case of IGRP.

Tip: Both RIP and IGRP also have methods to prevent routing loops such as maximum hop count, hold-down timers and poison-reverse.

RIP and IGRP are simple to configure on the router. For RIP the IOS command would be:

router rip

followed by the network statement or statements on the next line. For IGRP it's:

router igrp 10

which includes a chosen autonomous system number and the network statement or statements.

Tip: If two routers are configured with the IGRP routing protocol and they don't use the same autonomous system number, they won't exchange routing updates.

WAN Protocols
The typical CCNA may be called upon to configure routers for WAN links, so you'll want to know the primary WAN protocols and preferred use. One of those, frame relay, is a readily available packet-switching protocol widely supported by WAN providers. There are many things to configure to ready a frame relay connection, and you should be intimately familiar with them. Study and memorize the DLCI, LMI, encapsulation and use of subinterfaces.

Another popular WAN protocol is ISDN, with its many different configuration options -- much like frame relay. Know the ISDN protocols and reference points, and remember that it uses a circuit-switching method for network access.

What's the total bandwidth available with an ISDN BRI connection and how many channels are supported? The answer is two B channels of 64Kbps each and one D channel of 16Kbps for a total of 144Kbps.

Tip: If you need a refresher on WAN protocols, click here.

Tip: When troubleshooting ISDN configuration and connections, one of the most useful Cisco IOS commands is:

show isdn status

Don't forget about PPP (and its authentication methods) as a supporting WAN protocol. PAP uses clear-text, while CHAP supports many encrypted forms of network authentication without sending the password where it could be captured by others.

Network Management
Cisco requires a CCNA to know the network management protocols and methods for network access such as CDP and Access Lists. Know the different CDP commands and uses for determining Cisco devices on the network:

show cdp

You should be quite familiar with the structure, operation, verification and modification of standard and extended Access Lists. Know the ranges used for IP and IPX standard and extended lists, such as 1 through 99 for standard IP, 101 through 199 for extended IP, 800 through 899 for standard IPX, and 900 through 999 for extended IPX.

Tip: If you created an Access List with various deny statements and no permit, you'd prohibit the routing of all traffic on the applied interface. (Remember, there's an explicit deny at the end of each access list.)

LAN Design
If you thought that design holds no place in the CCNA's day-to-day work, think again. You need to be familiar with the three layers of the network design model, Core, Distribution and Access. Core is responsible for high-speed traffic switching and usually nothing more. The Distribution layer is the link between the Access and Core layers, and usually consists of routers and configuration of network policies, and possibly remote branch office connections. The Access layer is where users access the network through switches or workgroup hubs.

Another area of LAN design to concern yourself with deals with defining network congestion problems and preventing them. (Remember my earlier discussion on collision and broadcast domains?) You should also know the features, benefits and limitations of Fast Ethernet. Data can travel at 10Mbps or 100Mbps; with full-duplex transmission; data can travel simultaneously in both directions.

Tip: Remember that full-duplex Ethernet has a distance limitation of 100 meters, cabling type restrictions of category 5 and the need for network switches.

IOS from the Start
So where do you start when you're handed your first Cisco router and a slick new Pentium 4 laptop with wireless? You'll need to get up close and personal with the router by connecting it to your laptop's serial port with a Cisco official console cable or what's also commonly referred to as a rolled-cable (pin 1 to 8, 2 to 7, 3 to 6, and so on). Then you'll want to start up your favorite terminal emulator package and configure it for 9600bps, 8 bits, no parity, and 1 stop bit. After the router's command prompt has responded, you can begin your configuration. Most Cisco routers also want to begin with the Initial Configuration Dialog, or wizard as I call it. (If you enter "no" when prompted, you can go directly to the command prompt; you can always return to the wizard by typing "setup".) It might be of value to you the first or second time but eventually you will grab the command line by the horns unassisted.

From here you can enter into the privilege mode and be the master of your router's command line. To enter the privilege mode, type "enable"; enter the configuration mode by typing "config t". From here you can enable a password. Type:

enable secret mypassword

The enable secret command encrypts the password when it's displayed in the configuration. Now configure the VTY line password and the Console password to keep others from accessing the router through those connections. The VTY lines are used when telnetting to the router from the network; if login and passwords aren't configured, you'll always have to return to the dark and musty wiring closet to connect through the console port with the rolled-cable. Type:

line vty 0 4
login
password mypassword

Now on to the console port, should anyone else enter the wiring closet and attempt to change your router's configuration. Type:

line console 0
login
password mypassword.

You can also assign a name to the router for later identification when connecting through the network. Type:

hostname myrouter

Tip: If you make mistakes while entering commands, there are a few editing commands you should remember:

• Ctrl-A takes you to the beginning of line
  
• Ctrl-E takes you to the end of the line
  
• Up arrow and down arrow and Page Up and Page Down show previous commands.

Better yet type, "show history" and select from the list.

Now you can move on to the router's interface configurations. First, enter the interface configuration mode by typing:

interface ethernet 0 or interface serial 0

Then assign an IP or IPX addresses by typing:

ip address 192.168.1.1 255.255.255.0

For IPX assign the network number by typing:

ipx network 10

Don't forget to issue the no shutdown command to enable the interface.

Tip: Remember, for classfull routing protocols such as RIP and IGRP, all of your configured interfaces subnet masks must match on each router of the internetwork.

Now you can type "exit" to back out of the configuration mode and save your configuration by typing:

copy running-config startup config

Use:

copy running-config tftp

or

copy tftp running-config

to copy your configuration to a network server or from the server to your router.

Tip: Before copying your configuration to a network TFTP server, verify space exists on the server's disk and that the router can ping the server. Use:

copy flash tftp

or

copy tftp flash

to back up the IOS image or to copy a new IOS image to the router. Remember that your IOS image is stored in Flash memory and the running configuration is stored in RAM, but your startup configuration is stored in NVRAM.

Hook up your freshly-configured router to your network's switch or hub with a straight-through network cable. (Be sure you know the different cable wiring types for the new exam such as straight-through, crossover and rolled.) Now you're ready to leave the dark, musty wiring closet and return to your comfortable office knowing the router is performing its job. Then it's time to find a highly-visible location for your new Cisco CCNA certificate. Good luck!

Andy Barkl, an MCT, MCSE+I, MCSA, certified also as a CCDA, CCNP, and A+, i-Net+, Network+, Server+ expert instructor, has more than 18 years of experience in the IT field. He is the owner of MCT & Associates LLC in Phoenix, Ariz. He is the online editor for MCPMag.com, TCPMag.com and a contributing editor for Coriolis and Sybex. He can be reached at andy.barkl@wetrainit.com You can contact Andy about "Making Your Mark with the New CCNA " at andy.barkl@wetrainit.com.