Foundation Summary

The Foundation Summary section of each chapter lists the most important facts from the chapter. Although this section does not list every fact from the chapter that will be on your CCNA exam, a well-prepared CCNA candidate should know, at a minimum, all the details in each Foundation Summary section before going to take the exam. The terms connection-oriented and connectionless have some relatively well-known connotations inside the world of networking protocols. The meaning of the terms is...

Final Lab Scenario

The current CCNA exams include simulated lab questions. The best way to prepare for those is to work with live networks using Cisco routers and switches. You should also make sure to do all the questions in the testing engine on the CD, as it contains a large number of simulated lab questions. You can also use the NetSim network simulator on the CD, or rent time via online labs. Regardless of how much time and effort you spend with hands-on practice, the following lab scenario can help you with...

Address Resolution Protocol and the Domain Name System

Network designers should try to make using the network as simple as possible. At most, users might want to remember the name of another computer with which they want to communicate, such as remembering the name of a web site. They certainly do not want to remember the IP address, nor do they want to try to remember any MAC addresses So, TCP IP needs to have protocols that dynamically discover all the necessary information to allow communications, without the user knowing more than a name. You...

Analog Modems

Analog modems allow two computers to send and receive a serial stream of bits, with no physical changes required on the typical analog local loop between a residence and the telco CO. Because the switch in the CO expects to send and receive analog voice signals over the local loop, modems simply send an analog signal to the PSTN and expect to receive an analog signal from the PSTN. However, that analog signal represents some bits that the computer needs to send to another computer, instead of...

ATM and SONET

Asynchronous Transfer Mode (ATM) and Synchronous Optical Network (SONET) together provide the capability for a telco to provide high-speed services for both voice and data over the same network. SONET defines a method for transmitting digital data at high speeds over optical cabling, and ATM defines how to frame the traffic, how to address the traffic so that DTE devices can communicate, and how to provide error detection. In short, SONET provides Layer 1 features, and ATM provides Layer 2...

Balanced Hybrid Protocols Enhanced IGRP

EIGRP does not use distance vector or link-state logic, but instead it uses a whole new category of routing protocol. This new category has some features similar to link-state protocols, others similar to distance vector protocols, and yet others unlike either of the two. Cisco sometimes categorizes EIGRP as a balanced hybrid protocol, so you should remember the term. The internal workings of EIGRP depend on an algorithm called the Diffusing Update Algorithm (DUAL). DUAL exchanges more topology...

Basic Administrative Configuration

Chapter 7 focused on the configuration process more than the actual configuration commands that happened to be in the chapter. Before you configure IP, this short section reviews some of the basic commands you typically will configure on any router. On most routers, you would configure at least the following Reference to a DNS so that commands typed on the router can refer to host names instead of IP addresses Set a password for those Telnetting to the router Set the enable secret password to...

Boot Protocol BOOTP

Dynamic Host Configuration Protocol (DHCP) RARP and BOOTP work using the same basic process. To use either protocol, a PC needs a LAN interface card. The computer sends a LAN broadcast frame announcing its own MAC address and requests that someone assign it an IP address. Figure 5-11 outlines the process for both RARP and BOOTP. Hey Everybody My MAC Address Is 0200.1111.1111. If You Are a RARP Server, Please Tell Me My IP Address 0200.1111.1111 10.1.1.1 0200.1234.567810.1.1.2 0200.5432.1111...

Cable Modem Summary

Like DSL, cable modems bring high-speed remote access capabilities to the home. The speeds might seem astounding 30 to 40 Mbps downstream is indeed impressive. In fact, I had a cable modem a few years ago and was one of the first people in my neighborhood to get it. I surfed the web much faster from home than I did from the local Cisco Systems office The data service is always on, even when someone is watching TV. Because it doesn't use the telephone line at all, you also can use the phone at...

Cable Modems

Of all the access technologies covered in this chapter, cable modems are the only one not using a phone line from the local telco for physical connectivity. Many homes also have a cable TV service supplied by an analog electrical signal entering the home over a coaxial cable in other words, over the cable TV cabling. Cable modems provide an always-on Internet access service, while allowing you to surf the Internet over the cable and make all the phone calls you want over your telephone line and...

Cabling and Connectors

Practically every other Cisco certification exam ignores the topic of cabling those exams just assume that you can read the manuals and figure out what cables are needed. Interestingly, a well-designed cabling plan, with the right cables, can be a big component of making a LAN more manageable and available. So, cabling is indeed important in real networks. The cables themselves contain different components inside the cable you just have to cut one open to look inside to see internal components....

Cidr

CIDR is a convention defined in RFC 1817 (www.ietf.org rfc rfc1817.txt) that calls for aggregating multiple network numbers into a single routing entity. CIDR actually was created to help the scalability of Internet routers imagine a router in the Internet with a route to every Class A, B, and C network on the planet There are actually a little more than two million Class C networks alone By aggregating the routes, Internet routers have a significantly smaller number of routes in their routing...

Cisco ISL

Cisco created ISL before the IEEE standardized a trunking protocol. Because ISL is Cisco proprietary, it can be used only between two Cisco switches. ISL fully encapsulates each original Ethernet frame in an ISL header and trailer, with the encapsulated original Ethernet frame being unchanged. Figure 10-4 shows the framing for ISL. The ISL header includes several fields, but most important, the ISL header VLAN field provides a place to encode the VLAN number. By tagging a frame with the correct...

Cisco Published Intro Exam Topics Covered in This Part

1 Use a subset of Cisco IOS commands to analyze and report network problems 2 Use embedded layer 3 through layer 7 protocols to establish, test, suspend or disconnect connectivity to remote devices from the router console 4 Establish communication between a terminal device and the router IOS, and use IOS for system analysis 5 Manipulate system image and device configuration files 6 Perform an initial configuration on a router and save the resultant configuration file 7 Use commands incorporated...

CLI Help Features

If you printed the IOS Command Reference documents, you would end up with a stack of paper several feet tall. No one should expect to memorize all the commands and no one does in real life, either. Several very easy, convenient tools can be used to help you remember commands and then also save you time typing. As you progress through your Cisco certifications, the exams will cover progressively more commands. However, you should know the methods of getting command help. Table 7-3 summarizes...

Command Syntax Conventions

The conventions used to present command syntax in this book are the same conventions used in the Cisco IOS Command Reference. The Command Reference describes these conventions as follows Vertical bars (I) separate alternative, mutually exclusive elements. Square brackets indicate optional elements. Braces indicate a required choice. Braces within brackets indicate a required choice within an optional element. Boldface indicates commands and keywords that are entered literally as shown. In...

Comparing and Contrasting IP Routing Protocols

Routing protocols can be categorized in several ways. One distinction is whether the protocol is more useful between two companies or inside a single company. Only one IP routing protocol that is popular today, the Border Gateway Protocol (BGP), is designed specifically for use between two different organizations. In fact, BGP distributes routing information between ISPs worldwide today and between ISPs and their customers as need be. Routing protocols that are best used to distribute routes...

Configuring Cisco IOS Software

You must understand how to configure a Cisco router to succeed on the exam or to succeed in supporting Cisco routers. This section covers the basic configuration processes, including the concept of a configuration file and the locations in which the configuration files can be stored. Configuration mode is another mode for the Cisco CLI, similar to user mode and privileged mode. User mode allows commands that are not disruptive to be issued, with some information being displayed to the user....

Configuring IP Addresses

You easily can configure a Cisco router to forward IP traffic when you understand IP addressing and the IOS configuration process described in Chapter 7, Operating Cisco Routers. This chapter shows you examples of a variety of commands used to configure and troubleshoot the routing of IP packets in a Cisco router. Tables 13-2 and 13-3 summarize many of the most common commands used for IP configuration and verification. You can refer to other sources for more information about basic IP...

Connection Establishment and Termination

TCP connection establishment occurs before any of the other TCP features can begin their work. Connection establishment refers to the process of initializing sequence and acknowledgment fields and agreeing to the port numbers used. Figure 6-8 shows an example of connection establishment flow. Figure 6-8 TCP Connection Establishment SYN, ACK, DPORT 1027, SPORT 80 < - SEQ 201, ACK 1451 ACK, DPORT 80, SPORT 1027 This three-way connection-establishment flow must complete before data transfer can...

Considerations When Using Net Sim

NetSim is a wonderful product, and you can certainly get a lot of good hands-on experience using the NetSim product that is included with the book. However, like any simulator product, it does not mimic a network with 100 accuracy. Some situations are difficult to simulate. For instance, it is very challenging to simulate the output of debug commands, because the simulator is not actually running IOS. If you intend to use NetSim, please download the latest list of hints, tips, and caveats from...

Converting Analog Voice to Digital Voice

The last step in understanding how the PSTN supports voice across a digital PSTN relates to how the PSTN converts the analog electrical signals to digital signals, and vice versa. To see the need for the conversion, examine Figure 15-4. Figure 15-4 Analog Voice Calls Through a Digital PSTN Figure 15-4 Analog Voice Calls Through a Digital PSTN When Andy calls Barney in Raleigh, the circuit is set up by the telco. (Yes, Barney moved to Raleigh since the last example.) And it works It works...

Data Link Function 4 Identifying the Encapsulated Data

Finally, the fourth part of a data link identifies the contents of the Data field in the frame. Figure 3-3 helps make the usefulness of this feature apparent. The figure shows a PC that uses both TCP IP to talk to a web server and Novell IPX to talk to a Novell NetWare server. Figure 3-3 Multiplexing Using Data-Link Type and Protocol Fields When PC1 receives data, should it give the data to the TCP IP software or the NetWare client software Of course, that depends on what is inside the Data...

Data Link Layer Fundamentals Ethernet LANs

As you learned in the previous chapter, OSI Layers 1 and 2 map closely to the network interface layer of TCP IP. In this chapter, you will learn more details about the functions of each of the two lowest layers in the OSI reference model, with specific coverage of Ethernet local-area networks (LANs). The introduction to this book mentioned that the INTRO exam covers some topics lightly and covers others to great depth. As implied in the title, this chapter hits the fundamentals of Ethernet,...

Digital Subscriber Line

Any two computers using compatible modems could communicate with each other. Those computers might just be two PCs, a PC dialing into a router or access server at one of the business offices, or a PC dialing into a router or access server at an ISP. As long as both endpoints have a compatible modem, the two can communicate. By the time DSL came around in the mid- to late 1990s, the main goal for remote access was not the capability to connect to any site anywhere, but to connect to either the...

Distance Vector Protocols RIP and IGRP

Distance vector protocols advertise routing information by sending messages, called routing updates, out the interfaces on a router. These updates contain a series of entries, with each entry representing a subnet and a metric. The metric represents how good the route is from that router's perspective, with a smaller number being a better route. Any routers that receive a copy of a distance vector routing update receive that information and possibly add some routes to their routing table. The...

Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide whether you really need to read the entire chapter. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. The ten-question quiz, derived from the major sections in Foundation Topics portion of the chapter, helps you determine how to spend your limited study time. Table 3-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz questions...

DSL Protocols

DSL itself provides a Layer 1 transmission path between two endpoints, in some ways like the Layer 1 service that analog modems and ISDN modems provide. However, DSL uses some additional protocols to support data transfer. For instance, DSL uses ATM as the Layer 2 protocol between the DSL router or DSL modem in the home and the ISP router. Additionally, DSL uses a protocol called PPP over ATM (PPPoA). PPP and ATM are both data-link protocols, but they serve different purposes. PPP provides...

Error Recovery Reliability

TCP provides for reliable data transfer, which is also called reliability or error recovery, depending on what document you read. To accomplish reliability, TCP numbers data bytes using the Sequence and Acknowledgment fields in the TCP header. TCP achieves reliability in both directions, using the Sequence Number field of one direction combined with the Acknowledgment field in the opposite direction. Figure 6-5 shows the basic operation. In Figure 6-5, the Acknowledgment field in the TCP header...

Ethernet 10BASET Cabling

The PCs and hub in Figure 3-5 typically use Category 5 UTP cables with RJ-45 connectors, as shown in Figure 3-2. The Ethernet cards in each PC have an RJ-45 connector, as does the hub these connectors are larger versions of the same type of connector used for telephone cords between a phone and the wall plate in the United States. So, connecting the Ethernet cables is as easy as plugging in a new phone at your house. The details behind the specific cable used to connect to the hub are important...

Fiber Optic Cabling and Connectors for Ethernet

Fiber cabling, also called optical cabling or fiber optics, provides another option for cabling Ethernet. The main differences, in terms of function, between optical cabling for Ethernet and electrical cabling are as follows Longer distances supported by optical cabling Less magnetic interference, making it slightly more secure Only type of cabling supported by 10 Gig Ethernet For instance, network engineers might choose to use optical interfaces and cabling for Ethernet when building a campus...

Final Preparation

So, you have made it through most of the book, and you have probably either scheduled your INTRO exam or CCNA exam, or at least thought about when you want to try to take it. Congratulations for getting this far You will soon have finished your first step toward building your networking career r sum . This chapter provides some tips on your final preparation for the exam. It also provides an example scenario, which helps you to pull many of the hands-on skills together into a single review...

Flow Control Using Windowing

TCP implements flow control by taking advantage of the Sequence and Acknowledgment fields in the TCP header, along with another field called the Window field. This Window field implies the maximum number of unacknowledged bytes allowed outstanding at any instant in time. The window starts small and then grows until errors occur. The window then slides up and down based on network performance, so it is sometimes called a sliding window. When the window is full, the sender will not send, which...

Frame Relay

Point-to-point WANs can be used to connect a pair of routers at multiple remote sites. However, an alternative WAN service, Frame Relay, has many advantages over point-to-point links, particularly when you connect many sites via a WAN. To introduce you to Frame Relay, I focus on a few of the key benefits compared to leased lines. One of the benefits is seen easily by considering Figures 4-7. Figure 4-7 Two Leased Lines to Two Branch Offices In Figure 4-7, a main site is connected to two branch...

Full Duplex Ethernet

Full-duplex Ethernet was explained back in Chapter 3. Briefly, when a switch port has only a single device attached to it, no collisions could possibly occur because there is only one connected device. So, the device cabled to that switch port disables its NIC loopback logic, allowing the device to both send a frame and receive a frame at the same time. If a hub with multiple devices is connected to a switch port, collisions still can occur, so half-duplex operation must be used. Figure 9-6...

Fundamentals of IP

The OSI model assigns the functions of path selection and logical addressing to the OSI network layer (Layer 3). Path selection includes the process of learning all the paths, or routes, in a network and then forwarding packets based on those paths or routes. Often the terms path selection and routing are used interchangeably. In most Cisco documentation and in this book, routing is the more popular term. In this chapter, you will learn about the core concepts behind OSI Layer 3. Because CCNA...

Fundamentals of TCP and UDP

The Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are the two most popular TCP IP transport layer protocols. These TCP IP protocols define a variety of functions considered to be OSI transport layer, or Layer 4, features. Some of the functions relate to things you see every day for instance, when you open multiple web browsers on your PC, how does your PC know which browser to put the next web page in When a web server sends you 500 IP packets containing the various parts...

How Spanning Tree Works

The Spanning Tree Algorithm places each bridge or switch port into either a forwarding state or a blocking state. All the ports in the forwarding state are considered to be in the current spanning tree. The collective set of forwarding ports creates a single path over which frames are sent between Ethernet segments. Switches can forward frames out ports and receive frames in ports that are in a forwarding state switches do not forward frames out ports and receive frames in ports that are in a...

How to Use This Book to Prepare for the Intro Exam

To study for the INTRO exam, you can simply use this book and start reading. The study plan is simple. However, if you have some experience or knowledge of Cisco products and networking protocols already, you might be able to save a little study time while taking only small risks. Figure I-1 shows the progression you should take through the books as you prepare for the INTRO exam. In each chapter, an assessment quiz, called the Do I Know This Already Quiz, helps you decide whether you already...

How You Should Proceed with Net Sim

You can bring up NetSim and dive right in. However, here a a few suggestions before you are Bring up NetSim now, and make sure you can at least get to a router command prompt, using the PC you will most likely use when studying. That way, when you are ready to do your first lab or scenario, you know you have worked out any installation issues. If you intend to do most of the labs and scenarios, you might want to print CD-only Appendixes B and C. Decide if you prefer to do the labs and scenarios...

Internal Processing on Cisco Switches

Switches use a couple of different types of internal processing variations. Almost of the more recently released switches use store-and-forward processing, but all three types of switching are supported in at least one type of currently available Cisco switch. Some switches, and transparent bridges in general, use store-and-forward processing. With store-and-forward, the entire frame is received by the switch before the first bit of the frame is forwarded. However, Cisco also offers two other...

IP Addressing and Subnetting

In Chapter 5, Fundamentals of IP, you learned about the basic concepts and terminology relating to IP addressing. These concepts were introduced early in the book because your understanding of many basic networking concepts depends on a base knowledge of IP addressing. In this chapter, you will learn about the concepts and mathematics that let you analyze IP addresses and subnets. IP addressing is the only major topic that happens to get coverage on both of the INTRO and ICND exams. To answer...

IP Addressing Definitions

If a device wants to communicate using TCP IP, it needs an IP address. When the device has an IP address and the appropriate software and hardware, it can send and receive IP packets. Any device that can send and receive IP packets is called an IP host. IP addresses consist of a 32-bit number, usually written in dotted-decimal notation. The decimal part of the term comes from the fact that each byte (8 bits) of the 32-bit IP address is converted to its decimal equivalent. The four resulting...

IP Addressing Fundamentals

No one reading this book should be shocked to hear that IP addressing is one of the most important topics for passing the the INTRO and ICND exams. In fact, IP addressing is the only major topic that is covered specifically on both the INTRO and ICND exams. Plus, you need a comfortable, confident understanding of IP addressing and subnetting for success on any Cisco certification. In other words, you had better know addressing and subnetting This section introduces IP addressing and subnetting,...

IP Addressing Review

Chapter 5 explained the concepts behind IP addressing Class A, B, and C networks and subnetting. Before looking at the math behind IP addressing, a quick review will be helpful. Many different Class A, B, and C networks exist. Table 12-2 summarizes the possible network numbers, the total number of each type, and the number of hosts in each Class A, B, and C network. Table 12-2 List of All Possible Valid Network Numbers* Table 12-2 List of All Possible Valid Network Numbers* Size of Network Part...

IP Naming Commands

When using the IOS CLI, you will want to refer to names instead of IP addresses. Particularly for the trace, ping, and telnet commands, the IP address or host name must be supplied. This section describes the use of host names on an IOS-based device. Along the way, some nuances of the use of Telnet are covered. IOS can use statically configured names as well as refer to one or more DNSs. Example 13-9 shows some names statically configured, with configuration pointing to two different DNSs....

IP Routing Protocols

IP routing protocols fill the IP routing table with valid, (hopefully) loop-free routes. Each route includes a subnet number, the interface out which to forward packets so that they are delivered to that subnet, and the IP address of the next router that should receive packets destined for that subnet (if needed). Before examining the underlying logic, you need to consider the goals of a routing protocol. The goals described in the following list are common for any IP routing protocol,...

IP Subnetting

IP subnetting creates vastly larger numbers of smaller groups of IP addresses, compared with simply using Class A, B, and C conventions. The Class A, B, and C rules still exist but now a single Class A, B, or C network can be subdivided into many smaller groups. Subnetting treats a subdivision of a single Class A, B, or C network as if it were a network itself. By doing so, a single Class A, B, or C network can be subdivided into many nonoverlapping subnets. Figures 12-2 and 12-3 show the basic...

ISDN Call Setup and Data Link Protocols

Call setup differs between ISDN and modems. With a telephone call and with analog modems, DTMF tones are sent across the analog local loop to the telco. The telco switch at the local CO interprets the dialed digits and sets up the call. However, with ISDN, there is no analog local loop over which the analog DTMF tones can be sent. ISDN devices send and receive signaling messages to and from the local ISDN switch to which it is connected. In telco terminology, signaling refers to any type of...

LAN Cabling Standards and Topologies

This chapter completes the Ethernet puzzle for this book, in relation to the requirements of the INTRO exam. Ethernet was covered in several other chapters of this book specifically, Chapter 3, Data Link Layer Fundamentals Ethernet LANs, Chapter 9, Cisco LAN Switching Basics, and Chapter 10, Virtual LANs and Trunking. The topics in those chapters laid the foundation of a relatively broad knowledge of Ethernet. However, to keep those chapters flowing and not get bogged down in some long tangents...

LAN Switching

Before bridges were created, a 10BASE-T network might have begun to suffer from performance problems. As described in the previous section, to improve performance, you might have added a two-port bridge, created two LAN segments, doubled the bandwidth, reduced collisions, and improved performance. Now take a step back and think about what might happen to that network with the bridge 6 months later. More devices have been added to the segments on each side of the bridge. More bandwidth-hungry...

Link State Protocols OSPF and Integrated ISIS

Link-state and distance vectors share a common goal to fill the routing tables with the current best routes. They differ significantly in how they each accomplish the task. The largest difference between the two is that distance vector protocols advertise sparse information in fact, distance vector protocols know only that other routers exist if the other router broadcasts a routing update to them. When a distance vector protocol in a router hears a routing update, the update says nothing about...

Listing of the Handson Exercises

To best use NetSim, you should first pick a particular lab or scenario. You might even want to print a copy if the lab or scenario is in one of the CD-only appendixes. Then you can bring up NetSim and select the corresponding NetSim lab topology that matches the lab or scenario. NetSim creates a simulated network that matches the lab or scenario, so all you have to do is start entering commands, just as if it were a real network with real gear The scenarios and labs are located in a couple...

Modem Installation and Cabling

PC modems can be located internally or externally. Internal modems are placed inside the PC itself, whereas external modems are external to the PC. Laptops might come with a modem built in or simply might use a convenient type of internal modem called a PCMCIA card, or simply PC card. PC cards are roughly the size of a credit card and easily can be inserted and removed from a PC. Most PC hardware comes with either a serial communications port, called a COM port, or a Universal Serial Bus (USB)...

OSI Reference Model

To pass the INTRO 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 you simply cannot typically walk down the hall and use a computer whose main, or even optional, networking protocols conform to OSI. OSI is the Open System Interconnection reference model for communications. Some...

OSI Terminology

First, remembering the names of the OSI layers is just an exercise in memorization. You might benefit from the following list of mnemonic phrases, with the first letters in each word being the same as the first letters of the OSI layer names, in order 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) You also should know how to use the names of the layers when discussing...

TCPIP 311

Chapter 12 IP Addressing and Subnetting 313 Do I Know This Already Quiz 313 Foundation Topics 319 IP Addressing Review 319 IP Subnetting 321 Analyzing and Interpreting IP Addresses and Subnets 323 Math Operations Used to Answer Subnetting Questions 324 Converting IP Addresses from Decimal to Binary, and Back Again 324 The Boolean AND Operation 326 Prefix Notation 328 How Many Hosts, and How Many Subnets 329 What Is the Subnet Number, and What Are the IP Addresses in the Subnet 333 Finding the...

Perspectives on the PSTN

The Public Switched Telephone Network (PSTN) was built to support traffic between telephones in other words, voice traffic. Three of the four access technologies covered in this chapter happen to use the PSTN, so a basic understanding of the PSTN can help you appreciate how modems, ISDN, and DSL work. If you already know a fair amount about the PSTN, feel free to jump ahead to the section titled Analog Modems. Sound waves travel through the air by vibrating the air. The human ear hears the...

Pointto Point Protocol

The International Telecommunications Union (ITU), then known as the Consultative Committee for International Telecommunications Technologies (CCITT), first defined HDLC. Later, the Internet Engineering Task Force (IETF) saw the need for another data-link protocol for use between routers over a point-to-point link. In RFC 1661, the IETF created the Point-to-Point Protocol (PPP). Comparing the basics, PPP behaves exactly like HDLC. The framing looks identical. There is an address field, but the...

Preparing for the Actual Exam Experience

For some of you, either the INTRO exam or the CCNA exam will be your first experience with a proctored computer-based exam for Cisco certification. Do not be alarmed it's not terribly different than using the exam software on the CD that came with the book. However, you should go into the exam day with the following in mind You typically need two forms of ID, at least one of which is a picture ID. A driver's license, a passport, and a military ID are all valid. The testing center is probably...

Qa

As mentioned in the introduction, you have two choices for review questions. The questions that follow give you a bigger challenge than the exam itself by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better and prove your conceptual and factual knowledge of this chapter. The answers to these questions are found in Appendix A. For more practice with exam-like question formats, including questions using a router...

Remote Access Technologies

Earlier in this book, you learned about Ethernet LANs, point-to-point WAN links, and Frame Relay. All of these technologies can be used to connect a corporate site to the Internet. However, none of these options is cost-effective for connecting the typical home-based user to the Internet. In this chapter, you will learn about several different technologies used for Internet access from the home. Some of these same technologies can be used to remotely access corporate networks as well. This...

Routing Path Selection

Routing focuses on the end-to-end logic of forwarding data. Figure 5-1 shows a simple example of how routing works. The logic seen in the figure is relatively simple. For PC1 to send data to PC2, it must send something to R1, when sends it to R2, then on to R3, and finally to PC2. However, the logic used by each device along the path varies slightly. PC1's Logic Sending Data to a Nearby Router In this example, PC1 has some data to send data to PC2. Because PC2 is not on the same Ethernet as...

Routing Protocol Overview

IP routing protocols have one primary goal to fill the IP routing table with the current best routes it can find. The goal is simple, but the process and options can be complicated. Terminology can get in the way when you're learning about routing protocols. This book's terminology relating to routing and routing protocols is consistent with the authorized Cisco courses, as well as with most Cisco documentation. So, just to make sure you have the terminology straight before diving into the...

Scenario Part A Planning

This scenario has three parts, listed as Parts A, B, and C. Part A begins with some planning guidelines that mainly consist of planning an IP addressing scheme for a network. After you complete Part A, Part B of the scenario asks you to configure the three routers and one switch to implement the planned design. Finally, Part C asks you to examine router command output and answer questions about the details of current operation of the network. Part C also lists some questions related to the user...

Scenario Part C Verification and Questions

The INTRO exam tests you on your memory of the kinds of information you can find in the output of various show commands. Using Examples 16-5, 16-6, and 16-7 as references, answer the questions following the examples. NOTE In the network from which these commands were captured, several administrative settings not mentioned in the scenario were configured. For example, the enable password was configured. So, the configurations might contain additional items not specifically mentioned in the...

Speed and Autonegotiation

Ethernet autonegotiation uses a process by which a switch and an Ethernet NIC together determine the best combination of parameters for that particular link. To support autonegotiation, the switch and the NIC must support multiple speeds, and they also probably support both half and full duplex. So, a 10 100 card connected to a switch can negotiate to use full-duplex 100 Mbps. If the next switch port is connected to a 10-Mbps-only card that does not even support autonegotiation, the switch will...

Step 3 R2 processes the incoming frame and forwards the packet to R3R2

Repeats the same general process as R1 when it receives the HDLC frame. After stripping the HDLC header and trailer, R2 also needs to find the routing table entry that matches destination 150.150.4.10. R2's routing table has an entry for 150.150.4.0, outgoing interface serial1, to next-hop router 150.150.3.1, which is R3. Before R2 can complete the task, the correct DLCI for the VC to R3 must be decided. The details of how R2 knows the right DLCI are covered in Chapter 11, Frame Relay, of the...

Summary of Interior Routing Protocols

Before finishing your study for the ICND or CCNA exam, you will learn a lot more about RIP-1, IGRP, EIGRP, and OSPF. This chapter has introduced you to some of the key terms and points of comparison for these routing protocols, as well as a few others. Table 14-6 summarizes the most important points of comparison between the interior routing protocols, and Table 14-7 lists some of the key terminology. Table 14-6 Interior IP Routing Protocols Compared Summary Table 14-6 Interior IP Routing...

The Case for Bridging and Switching

To appreciate the need for LAN switches and the logic behind LAN switches, you must learn about devices called transparent bridges. Vendors began offering transparent bridges in the marketplace long before switches. And because switches act like bridges in many ways, it helps your understanding of switches to first understand how bridges work and why they were created in the first place. To appreciate the need for bridges, you must be reminded of the state of Ethernet networking before bridges...

The Cisco IOS Software Boot Sequence

Cisco routers perform the same types of tasks that a typical computer performs when you power it on or reboot (reload) it. Of course, most of us do not think about these details very often. The router performs some somewhat obvious steps, with one of those being tricky namely, the process of choosing the location of the software to load and use in the router. And that software might not be IOS. The boot process follows this basic litany 1. The router performs a power-on self-test (POST) to...

The debug and show Commands

By far, the most popular single IOS command is the show command. The show command has a very large variety of options, and with those options, you can find the status of almost every feature of IOS. Essentially, the show command lists facts about the router's operational status that the router already knows. Another less popular command is the debug command. The debug command actually tells the router to spend some CPU cycles to do things besides its normal functions, to provide the user with...

The Need for Spanning Tree

Without the Spanning Tree Protocol (STP), frames would loop for an indefinite period of time in networks with physically redundant links. To prevent looping frames, STP blocks some ports from forwarding frames so that only one active path exists between any pair of LAN segments (collision domains). The result of STP is good Frames do not loop infinitely, which makes the LAN usable. However, the network uses some redundant links in case of a failure, but not for balancing traffic. To avoid...

The Tcpip Internetwork Layer

Imagine that you just wrote a letter to your favorite person on the other side of the country and that you also wrote a letter to someone on the other side of town. It's time to send the letters. Is there much difference in how you treat each letter Not really. You put different addresses on the envelope for each letter because the letters need to go to two different places. You put stamps on both letters and put them in the same mailbox. The postal service takes care of all the details of...

The Tcpip Network Interface Layer

The network interface layer defines the protocols and hardware required to deliver data across some physical network. The term network interface refers to the fact that this layer defines how to connect the host computer, which is not part of the network, to the network it is the interface between the computer and the network. For instance, Ethernet is one example protocol at the TCP IP network interface layer. Ethernet defines the required cabling, addressing, and protocols used to create an...

The Transmission Control Protocol

Each TCP IP application typically chooses to use either TCP or UDP based on the application's requirements. For instance, TCP provides error recovery, but to do so, it consumes more bandwidth and uses more processing cycles. UDP does not do error recovery, but it takes less bandwidth and uses fewer processing cycles. Regardless of which of the two TCP IP transport layer protocols the application chooses to use, you should understand the basics of how each of the protocols works. TCP provides a...

The User Datagram Protocol

UDP provides a service for applications to exchange messages. Unlike TCP, UDP is connectionless and provides no reliability, no windowing, and no reordering of the received data. However, UDP provides some functions of TCP, such as data transfer, segmentation, and multiplexing using port numbers, and it does so with fewer bytes of overhead and with less processing required. UDP multiplexes using port numbers in an identical fashion to TCP. The only difference in UDP (compared to TCP) sockets is...

Typical Features of OSI Layer

The transport layer (Layer 4) defines several functions, the most important of which are error recovery and flow control. Routers discard packets for many reasons, including bit errors, congestion and instances in which no correct routes are known. As you have read already, most data-link protocols notice errors but then discard frames that have errors. The OSI transport layer might provide for retransmission (error recovery) and help to avoid congestion (flow control) or it might not. It...

Typical LAN Features for OSI Layer

The OSI physical layer, or Layer 1, defines the details of how to move data from one device to another. In fact, many people think of OSI Layer 1 as sending bits. Higher layers encapsulate the data and decide when and what to send. But eventually, the sender of the data needs to actually transmit the bits to another device. The OSI physical layer defines the standards used to send and receive bits across a physical network. To keep some perspective on the end goal, consider the example of the...

Typical Uses of ISDN

Routers frequently use ISDN to create a backup link when their primary leased line or Frame Relay connection is lost. Although the leased line or Frame Relay access link seldom fails, when it does, a remote site might be completely cut off from the rest of the network. Depending on the business goals of the network, long outages might not be acceptable, so ISDN could be used to dial back to the main site. The ICND exam covers ISDN as well, including the features and configuration used by...

Unshielded Twisted Pair and Shielded Twisted Pair Cabling and Connectors

The Telecommunications Information Associatation (TIA) defines standards for LAN cabling. For copper-wire LAN cabling, two main branches have been defined Unshielded twisted pair (UTP) Shielded twisted pair (STP) Figure 11-5 shows a conceptual diagram of each type of cable. The figure shows a side view of each cable and a straight-on view of a UTP cable. All the parts of the figure show the cable cut open so that you can see the internal components of the cables. Figure 11-5 UTP and STP Cable...

Upgrading a Cisco IOS Software Image into Flash Memory

IOS files typically are stored in Flash memory. Flash memory is rewriteable, permanent storage, which is ideal for storing files that need to be retained when the router loses power. Also, because there are no moving parts, there is a smaller chance of failure as compared with disk drives, which provides better availability. As you will read soon, IOS can be placed on an external TFTP server, but using an external server typically is done for testing in production, practically every Cisco...

WAN Connections from the Customer Viewpoint

The concepts behind a point-to-point connection are simple. However, to fully understand what the service provider does to build his network to support your point-to-point line, you would need to spend lots of time studying and learning. However, most of what you need to know about WANs for the INTRO exam relates to how WAN connections are implemented between the telephone company and a customer site. Along the way, you will need to learn a little about the terminology used by the provider. In...

Warning and Disclaimer

This book is designed to provide information about selected topics for the Introduction to Cisco Networking Technologies (INTRO) exam for the CCNA certification. Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied. The information is provided on an as is basis. The authors, Cisco Press, and Cisco Systems, Inc., shall have neither liability nor responsibility to any person or entity with respect to any loss or damages...

What Are the Other Subnet Numbers

The final general type of IP addresing and subnetting question covered in this chapter asks you to list all the subnets of a particular network. You could use a long process, which requires you to count in binary and convert many numbers from binary to decimal. However, because most people would either learn the shortcut or use a subnet calculator in their normal jobs, I decided to just show you the shortcut method for this particular type of question. First, the question needs a better...

INTRO Exam Topics

Carefully consider the exam topics posted by Cisco on its web site as you study, particularly for clues as to how deeply you should know each topic. The exam topics use action words that follow a quasi-standard called Bloom's Taxonomy of the Cognitive Domain. Bloom's taxonomy defines a standard for word usage for when educators create objectives for courses. Objectives written according to Bloom's taxonomy define what the learner (student) should be able to accomplish after taking the class....

Ciscos Motivation Certifying Partners

Cisco's primary motivation for creating CCNA and most of the other Cisco certifications is to help determine the skill levels of its partners. Cisco fulfills only a small portion of its orders through direct sale from Cisco most often, a Cisco reseller is involved. (Cisco calls resellers channel partners.) Also, Cisco encourages partners to perform most consulting and implementation services relating to Cisco products. While working heavily with partners, Cisco needed to know which partners...

Objectives and Methods

The most important and somewhat obvious objective of this book is to help you pass the INTRO exam or the CCNA exam. In fact, if the primary objective of this book were different, the book's title would be misleading However, the methods used in this book to help you pass the exams are also designed to make you much more knowledgeable about how to do your job. This book uses several key methodologies to help you discover the exam topics on which you need more review, to help you fully understand...

For More Information

If you have any comments about the book, you can submit those via the www.ciscopress.com web site. Just go to the web site, select Contact Us, and type in your message. Cisco might make changes that affect the CCNA certification from time to time. You should always check www.cisco.com for the latest detail. Also, you can look to www.ciscopress.com 1587200945, where we will publish any information pertinent to how you might use this book differently in light of Cisco's future changes. For...

Access to the CLI

Cisco uses the acronym CLI to refer to the terminal user command-line interface to the IOS. The term CLI implies that the user is typing commands at a terminal, a terminal emulator, or a Telnet connection. To access the CLI, use one of three methods, as illustrated in Figure 7-1. You access the router through the console, through a dialup device through a modem attached to the auxiliary port, or by using Telnet. The router has RJ-45 receptacles for both the console and the auxiliary port. The...

The Tcpip Transport Layer

The TCP IP application layer includes a relatively large number of protocols, with HTTP being only one of those. The TCP IP transport layer consists of two main protocol options the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP). To get a true appreciation for what TCP IP transport layer protocols do, read Chapter 6, Fundamentals of TCP and UDP. However, in this section, you will learn about one of the key features of TCP, which enables us to cover some more general...

The Tcpip Application Layer

Arguably, the most popular TCP IP application today is the web browser. Many major software vendors either have already changed or are changing their software to support access from a web browser. And thankfully, using a web browser is easy you start a web browser on your computer and select a web site by typing in the name of the web site, and the web page appears. What really happens to allow that web page to appear on your web browser These next few sections take a high-level look at what...

The Tcpip Protocol Architecture

TCP IP defines a large collection of protocols that allow computers to communicate. TCP IP defines the details of each of these protocols inside document called Requests For Comments (RFCs). By implementing the required protocols defined in TCP IP RFCs, a computer can be relatively confident that it can communicate with other computers that also implement TCP IP. An easy comparison can be made between telephones and computers that use TCP IP. I can go to the store and buy a phone from one of a...

F

She builds and connects the new hubs in the lab, just to prove the concept. It works She makes the (now shorter) cables, installs the hubs and cables, and is ready to test. She goes to a few representative PCs and tests, and it all works The first network has now been deployed. Wanting to surprise Poppa Fred, Pebbles writes a memo to everyone in the company, telling them how to use the soon-to-be-famous Fred Transfer Program to transfer files. Along with the memo, she...

Switch LEDs During POST

Power-On Self Test (POST) defines the series of steps that a device goes through to test the hardware and find out what is working before moving on to loading the operating system. POST processing is performed by boot code that is loaded into ROM. Because a full operating system has not yet been loaded when the switch performs POST, it needs a way to tell the human user if POST worked well, if it failed partly, or if the switch is totally unusable. To communicate the status, the switch uses the...

Cisco Discovery Protocol

The Cisco Discovery Protocol (CDP) discovers basic information about neighboring routers and switches, without needing to know the passwords for the neighboring devices. CDP supports any LAN, HDLC, Frame Relay, and ATM interface in fact, it supports any interface that supports the use of SNAP headers. The router or switch can discover Layer 2 and Layer 3 addressing details of neighboring routers without even configuring that Layer 3 protocol this is because CDP is not dependent on any...

Initial Configuration Mode

The 2950 switch OS uses the same concepts of an initial configuration dialogue as does a router. When the switch initializes and finds no configuration file in NVRAM, it presents the console user with a question, asking whether to enter the initial configuration dialogue. The only real difference between the router initial configuration dialogue and the 2950 switch initial configuration dialogue is in the things the switch lets you configure. Otherwise, the process is identical. Example 8-1...

Clock Rates DCE and DTE

When a network engineer needs to add a point-to-point leased line between two routers, he contacts a service provider and orders the circuit. As part of that process, the customer specifies how fast the circuit should run, in kilobits per second (kbps). While the circuit is being set up by the telco, the engineer purchases two CSU DSUs, installs one at each site, and configures each CSU DSU. He also cables each router to the respective CSU DSU using the cables shown in the previous section....

OSI Layer 1 for Pointto Point WANs

The OSI physical layer, or Layer 1, defines the details of how to move data from one device to another. In fact, many people think of OSI Layer 1 as sending bits. Higher layers encapsulate the data, as described in Chapter 2, The TCP IP and OSI Networking Models. No matter what the other OSI layers do, eventually the sender of the data needs to actually transmit the bits to another device. The OSI physical layer defines the standards and protocols used to create the physical network and to send...

OSI Networking Models

The term networking model, or networking architecture, refers to an organized description of all the functions needed for useful communications to occur. Individual protocols and hardware specifications then are used to implement the functions described in the networking model. When multiple computers and other networking devices implement these protocols, which, in turn, implement the functions described by the networking model, the computers can successfully communicate. You can think of a...