A

In Figure 5-4, the acknowledgment field in the TCP header sent by the Web server implies the next byte to be received this is called forward acknowledgment. The sequence number reflects the number of the first byte in the segment. In this case, each TCP segment is 1000 bytes in length the sequence and acknowledgment fields count the number of bytes. Figure 5-5 depicts the same scenario, but the second TCP segment was lost or in error. The Web server's reply has an ACK field equal to 2000,...

A a

Table 6-30 Scenario 6-1 IP Addresses Table 6-30 Scenario 6-1 IP Addresses Serial between Albuquerque and Yosemite Serial between Albuquerque and Seville Assuming the details established in Figure 6-23 and Table 6-30 for Scenario 6-1, complete or answer the following 1 Create the configurations to enable IP as described in Table 6-30. Choose IP addresses as appropriate. 2 Describe the contents of the routing table on Seville after the routers are installed and all interfaces are up but no...

Comment About Data Links

Because the routers build new data link headers and trailers, and because the new headers contain data link addresses, the routers must have some way to decide what data link addresses to use. An example of how the router determines which data link address to use is the IP Address Resolution Protocol (ARP) protocol. ARP is used to dynamically learn the data link address of some IP host. An example specific to TCP IP will be useful to solidify the concepts behind routing. Imagine that PC1 is...

Address Resolution Protocol

One common problem that CCNAs deal with on a regular basis is this Given some Layer 3 address, what is its corresponding Layer 2 address Address Resolution Protocol (ARP) is the process by which this question is answered for an IP host on a LAN. ARP is needed because to send an IP packet across some LAN, the data link header and trailer (which encapsulate the packet) must first be created. The source MAC address in this new header is known, but the destination MAC is not known in advance ARP is...

Answers to Scenario 51 IP Addressing and Subnet Calculation

Assuming that you had issued the commands in Example 5-28, the most specific network diagram would look like Figure 5-48. The clues that you should have found in the show commands are as follows The types and IP addresses of the interfaces on Fred were in the show interface and show ip interface brief command output. The subnets could be learned from the show ip route command or derived from the IP addresses and masks shown in the show interface command output. The neighboring router's IP...

Answers to Scenario 54 IPX Examination

Assuming the details established in Figure 5-46 and the command output in Example 5-29, Example 5-30, and Example 5-31 for Scenario 5-4, the show ipx interface brief command and show ipx route command are the best methods for learning the network numbers in Table 5-52 (Task 1, for this scenario). Table 5-52 IPX Networks in Scenario 5-4 Completed Chart Table 5-52 IPX Networks in Scenario 5-4 Completed Chart (Continued) Table 5-52 IPX Networks in Scenario 5-4 Completed Chart (Continued) Assuming...

Answers to Scenario 73 IP Filtering Sample

Many solutions could fulfill the criteria stipulated for this scenario. The solutions provided in Examples 7-24 and 7-25 attempt to filter packets as close to the source of the packet as possible. It is impossible to determine whether your correct solution is better than the one given here, or vice versa, without more information about traffic loads and business needs in the network. Comments shown inside the configurations in Example 7-24 and Example 7-25 provide most of the detailed...

Answers to Scenario 74 IPX Filtering

Refer to the network illustrated in Figure 7-14 and Examples 7-17 through 7-20 to establish the Scenario 7-4 design details and the context of the answers to the three tasks for this scenario. Task 1 for Scenario 7-4 asks you to characterize the traffic that is discarded due to the access lists used on Atlanta. Furthermore, you need to determine whether clients in the remote sites can access the servers in Atlanta. The answer is not obvious in this case. The extended access list is particularly...

Answers to Task 1 for Scenario

Given the design criteria and the network setup illustrated in Figure 5-45, this scenario requires tricky subnet masks because a Class C network is used and because subnetting is needed. Using Frame Relay subinterfaces, there will be a need for seven different subnets one for each Ethernet and one for each Frame Relay VC. If 3 subnet bits are used, eight mathematical possibilities exist for subnet numbers. However, one is the zero subnet and the other is the broadcast subnet. In this case, use...

Answers to Task 2 for Scenario

Based on the network design illustrated in Figure 3-22, Task 2 for Scenario 3-1 states that D'Artagnan sends a packet to Aramis (source group-1.local-M, destination group-4.local-M). D'Artagnan sends this packet inside an Ethernet frame to Router A. The following are the solutions to exercises 1 through 4 for Task 2. 1 The routing tables are as follows In Router A 2 Router A discards the Ethernet header and adds an HDLC header. Router B discards the HDLC header and adds an Ethernet header....

Answers to Task 3 for Scenario

Based on the network design illustrated in Figure 3-22, Task 3 for Scenario 3-1 states that D'Artagnan sends a packet to Porthos (source group-1.local-M, destination group-6.local-M). D'Artagnan sends this packet inside an Ethernet frame to Router A. The following are the solutions to exercises 1 through 4 for Task 3. 1 The routing tables are as follows In Router A 2 Router A discards the Ethernet header and adds a Frame Relay header. Router D discards the Frame Relay header and adds an...

Answers to Task 4 for Scenario

Task 4 for Scenario 6-2 requires consideration of the effects of split horizon. Split horizon logic considers subinterfaces to be separate interfaces, in spite of the fact that several subinterfaces share the same physical interface. Boston advertises about 10.1.4.0 in its RIP update only out its subinterface 1. All other routes in Boston's routing table were learned through RIP updates from Atlanta, via updates entering that same subinterface therefore, Boston will not advertise about those...

Binary Algorithm for Deriving the Broadcast Address

The binary algorithm to determine the broadcast address when using no subnetting or basic subnetting is a little trickier than the similar algorithm for finding the subnet number. The algorithm shown here is not really what computers use, but it is more instructive about how broadcast addresses are structured. It starts by repeating the binary algorithm for computing the subnet number and then adding two short steps. The algorithm is as follows Step 1 Write down the IP address in binary. Step 2...

Binary Algorithm for Deriving the Network Number No Subnetting in

When a computer needs to answer this same question, it performs a Boolean math operation called AND between the address in question and the mask. The result of the AND operation is that the host bits are masked out that is, changed to binary 0s. The binary process, with no subnetting, is as follows Step 1 Write down the IP address in binary. Step 2 Write down the default mask appropriate for the class of address, in binary, beneath the binary IP address from Step 1. Step 3 Record the results of...

Binary Algorithm for Deriving the Subnet Number Basic Subnetting

The binary algorithm to determine the subnet number, when using basic subnetting, is practically identical to the algorithm used when there is no subnetting. Again, the key is in knowing what subnet mask is in use. The binary process, with basic subnetting, is as follows Step 1 Write down the IP address in binary. Step 2 Write down the subnet mask used in this network, in binary, beneath the binary IP address from Step 1. Step 3 Record the results of the Boolean AND below the two numbers. Step...

Binary Algorithm for Deriving the Subnet Number Difficult Subnetting

Difficult subnetting is a term used in this book to denote subnetting when the mask is not all 255s and 0s. The decimal algorithm for calculating the subnet, when basic subnetting is in use, is more challenging. In fact, several math tricks come in handy so that the result can be calculated without thinking about binary math. However, starting with the binary algorithm is helpful. These difficult masks typically contain one of the values shown in Table 5-17. To speed up the process of examining...

Binary Algorithm for Deriving the Valid Subnets with Basic and Difficult Subnetting

This section details a binary algorithm you can use to derive the subnet numbers. With basic subnetting, you probably would not want to go through this much trouble. However, with difficult subnetting, the binary algorithm will be useful, at least until you become comfortable with the decimal algorithm. The following binary algorithm is valid for basic subnetting as well. Step 1 Reserve space to record a series of 32-bit numbers, one over the other. Also leave space between each nibble and byte...

Bridges Switches and LAN Design

Cisco folklore tells of the day in 1998 when Cisco's revenues from LAN switching and hub products exceeded router revenues. That event in Cisco's history was significant because most people in the marketplace thought of Cisco as that router company for a long time. In fact, Cisco would prefer to even shake the reputation as a great router switch hub company and instead be known for empowering the Internet generation, a catch-phrase from the company's television ads. So, if switches and hubs...

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 was actually 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 By aggregating the routes, fewer routes would need to exist in the routing table. For instance, consider Figure 5-24. Class C networks 198.0.0.0 through 198.255.255.0 (they may...

CIDR Private Addressing and NAT

When connecting to the Internet, using a registered network number or several registered network numbers is a very straightforward and obvious convention. With registered network numbers, no other organization connected to the Internet will have conflicting IP addresses. In fact, this convention is part of the reason the global Internet functions well. In the early and mid-1990s, concern arose that the available networks would be completely assigned so that some organizations would not be...

Cisco Discovery Protocol

Cisco Discovery Protocol (CDP) is used by Cisco routers and switches to ascertain basic information about neighboring routers and switches. You can use this information to learn addresses quickly for easier Simple Network Management Protocol (SNMP) management, as well as learn the addresses of other devices when you do not have passwords to log in to the other device. CDP is a Cisco proprietary protocol to support forwarding CDP messages over an interface, that interface must support SNAP...

Cl cl a a a n

Table 6-31 Scenario 6-2 IP Addresses Table 6-31 Scenario 6-2 IP Addresses Assuming the details established in Figure 6-24 and Table 6-31 for Scenario 6-2, complete or answer the following 1 Create the configurations to enable IP as described in Table 6-31. Do not enable a routing protocol. 3 Calculate the subnet broadcast address for each subnet. 4 Describe the contents of the RIP update from Boston sent to Atlanta also describe the contents of the RIP update from Atlanta to Charlotte.

Classes of Networks

Class A, B, and C networks provide three network sizes. By definition, all addresses in the same network have the same numeric value network portion of the addresses. The rest of the address is called the host portion of the address. Individual addresses in the same network all have a different value in the host parts of the addresses but have identical values in the network part. Class A networks have a 1-byte-long network part. That leaves 24 bits for the rest of the address, or the host...

Comparing Routing Protocols

Several routing protocols for TCP IP exist. IP's long history and continued popularity have called for the specification and creation of several different competing options. So, classifying IP routing protocols based on their differences is useful and also is a fair topic for exam questions. One major classification of IP routing protocols is whether they are optimized for creating routes inside one organization or routes between two or more interconnected organizations. Exterior routing...

Comparison of LAN Segmentation Using Bridges Switches and Routers

Cisco expects CCNAs to have command of the tradeoffs involved when designing campus LANs. One key consideration is to understand the different behavior when separating, or segmenting, LAN segments with some switching device. All the concepts related to LAN segmentation using bridges, switches, and routers are included in other parts of this chapter or in other chapters. However, the comparisons made in this section are important and would be missed if this book simply covered the technical...

Configuration of IPX

As seen in Chapter 5, enabling RIP and SAP on a router is very straightforward. The ipx routing command enables both in a router, and the ipx network command on an interface implies that RIP and SAP updates should be sent and listened for on those interfaces. Router Yosemite has been configured for RIP and SAP (see Figure 6-15). The command output in Example 6-21 shows the result of some RIP and SAP show and debug commands. (Do not forget the CCNA exam will ask questions about what commands can...

Configuration of RIP and IGRP

The CCNA exam requires you to understand RIP and IGRP configuration details. RIP and IGRP configuration requires an understanding of two subtle nuances namely, what the network command really implies and how the router interprets the network command. Other than these two details, configuration is relatively easy. Hands-on experience is the best way to fully learn the details of configuration. In lieu of that, this section lists commands, provides examples, and points out any tricky features....

Configuring Tunneling

Tunneling configuration is not very complicated if you remember the framing with the transport, encapsulation, and passenger protocols. A tunnel interface is created on each router at the ends of the tunnel. To accommodate the transport protocol, an IP address is used at the endpoints of the tunnel these IP addresses are used as the source and destination IP addresses of the encapsulated packets. The type of encapsulation protocol is configured there are six alternatives. Finally, the tunnel...

Contents at a Glance

Chapter 1 All About the Cisco Certified Network Associate Certification 2 Chapter 2 Cisco Internetwork Operating System (IOS) Fundamentals 20 Chapter 3 OSI Reference Model & Layered Communication 68 Chapter 4 Bridges Switches and LAN Design 128 Chapter 5 Network Protocols 210 Chapter 7 Understanding Access List Security 454 Chapter 8 WAN Protocols and Design 514 Chapter 9 Scenarios for Final Preparation 638 Appendix A Answers to the Do I Know This Already Quizzes and Q& A Sections 700...

D n

Example 7-16 Access List at Mayberry access-list 44 permit 180.3.5.13 0.0.0.0 interface serial 0 ip access-group 44 25 In an extended named IPX access list with five statements, a no version of the second statement is issued in configuration mode. Immediately following, another access list configuration command is added for the same access list. How many statements are in the list now, and in what position is the newly added statement 26 Name all the items that a named extended IPX access list...

Data Link Function 2 Addressing

Cisco requires that CCNAs master the formats and meanings of data link and network layer addresses. Addressing is needed on LANs because there can be many possible recipients of data that is, there could be more than two devices on the link. Because LANs are broadcast media a term signifying that all devices on the media receive the same data each recipient must ask the question, Is this frame meant for me With Ethernet and Token Ring, the addresses are very similar. Each uses Media Access...

Data Link Function 3 Error Detection

Error detection is simply the process of learning whether bit errors occurred during the transmission of the frame. To do this, most data links include a frame check sequence (FCS) or cyclical redundancy check (CRC) field in the data link trailer. This field contains a value that is the result of a mathematical formula applied to the data in the frame. The FCS value calculated and sent by the sender should match the value calculated by the receiver. All four data links discussed in this section...

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 3-13 helps make the usefulness of this feature apparent. Figure 3-13 Multiplexing Using Data Link Type and Protocol Fields When PC1 receives data, does it give the data to the TCP IP software or the NetWare client software Of course, that depends on what is inside the data field. If the data came from the Novell server, then PC1 hands the data off to the NetWare client code. If the data comes...

Decimal Algorithm for Deriving the Broadcast Address Difficult Subnetting

The decimal algorithm for deriving the broadcast address when difficult subnetting is used is shown next. When in doubt, use the binary algorithm. However, the following decimal algorithm will yield the correct results Step 1 Write down the IP address in decimal. Step 2 Write down the mask in decimal. Step 3 Examine the mask. One of the four octets will have a value besides 255 or 0 otherwise, this would not be considered to be a difficult case. The octet with the non-255, non-0 value is...

Decimal Algorithm for Deriving the Broadcast Address No Subnetting or Basic Subnetting

The algorithms, both binary and decimal, for deriving the broadcast addresses are similar to the same algorithms for deriving the subnet numbers. The algorithms used for basic subnetting are used as a basis for the following algorithms for deriving the broadcast addresses. First, the decimal algorithm is as follows Step 1 Write down the IP address in decimal. Step 2 Copy below the IP address either the first one, two, or three dotted decimal numbers of the address, based on whether the subnet...

Decimal Algorithm for Deriving the Subnet Number Basic Subnetting

The decimal algorithm, when basic subnetting is in use, is as follows Step 1 Write down the IP address in decimal. Step 2 Copy below the IP address either the first one, two, or three dotted decimal numbers of the address, based on whether the subnet mask is 255.0.0.0, 255.255.0.0, or 255.255.255.0, respectively. Step 3 For the remaining dotted decimal numbers, record decimal value 0. This algorithm is very similar to the algorithm that is used when there is no subnetting. The only difference...

Decimal Algorithm for Deriving the Subnet Number Difficult Subnetting

The decimal algorithm that I like best for difficult subnetting works well. However, this algorithm is not very helpful for understanding subnetting. So, if you understand subnetting and are willing to use the more time-consuming binary algorithm on the exam for the difficult cases, you may want to skip this section to avoid getting confused. The algorithm is as follows Step 1 Write down the IP address in decimal. Step 2 Write down the mask in decimal. Step 3 Examine the mask. One of the four...

Decimal Algorithm for Deriving the Valid Subnets with Basic and Difficult Subnetting

CCNAs will need to derive the valid subnets of a network on a regular basis, so a decimal algorithm to derive the valid subnets even when difficult subnetting is used proves invaluable. With some practice, you can use the following algorithm without pen and paper or a calculator. This algorithm works only if the subnet field is less than 8 bits. If the subnet field is larger, you can use a similar algorithm (which is not shown) once you understand this specific algorithm. The algorithm is as...

Decimal Algorithm for Deriving the Valid Subnets with Basic Subnetting

Time counts when taking the CCNA exam, so it's a good idea to take advantage of the easier decimal algorithms to derive facts about subnetting. The algorithm for deriving the subnet numbers of a network, given a static, basic mask, is extremely intuitive. Two cases for the decimal algorithm will be examined here a Class A network subnetted using mask 255.255.0.0, and a Class B network subnetted using mask 255.255.255.0 Step 1 Write down the 1 or 2 bytes of the network number. Step 2 Leave a...

Default Routes and the ip classless Command

Default route processing can be useful in several situations. Default route processing is a general term that refers to the choices that the router can make when no match exists between the routing table and the destination address of a packet. Without any default routes, a packet whose destination is not matched in the routing table is discarded. Figure 5-31 shows a typical case in which some form of default route would be useful. R1, R2, and R3 are connected to the rest of this network only...

Distance Vector Routing

CCNAs deal with routing problems on a daily basis some of these problems are a result of the logic behind distance vector routing protocols. To understand what distance vector routing means is to understand how a routing protocol accomplishes the following goals Learning routing information Adding the current best route after one has failed The following list summarizes the behavior of a router that uses the RIP-1 or IGRP distance vector routing protocols Directly connected subnets are already...

Do I Know This Already Quiz

The purpose of the Do I Know This Already quiz is to help you decide what parts of this chapter to use. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. This 12-question quiz helps you determine how to spend your limited study time. The quiz is sectioned into four smaller four-question quizlets, which correspond to the four major headings in the Foundation Topics section of the chapter. Figure 3-1 outlines suggestions on how to spend...

Example Layer 3 Address Structures

Each Layer 3 address structure contains at least two parts. One (or more) part at the beginning of the address works like the ZIP code and essentially identifies the grouping. All instances of addresses with the same value in these first bits of the address are considered to be in the same group for example, the same IP subnet or IPX network or AppleTalk cable range. The last part of the address acts as a local address, uniquely identifying that device in that particular group. Table 3-10...

Fast Ethernet and Gigabit Ethernet

The two key additional features of Fast Ethernet, as compared to 10-Mbps Ethernet, are higher bandwidth and autonegotiation. Autonegotiation allows an Ethernet card, hub, or switch to determine which type of 100-Mbps Ethernet is supported by the device, hub, or switch on the other end of the cable. Also, support for half duplex or full duplex is negotiated. If the other device, such as a 10BaseT NIC, does not support autonegotiation, then autonegotiation will settle for half-duplex 10BaseT....

Figure Icons Used in This Book

Throughout the book, you will see the following icons used for networking devices Throughout the book, you will see the following icons used for peripherals and other devices. Throughout the book, you will see the following icons used for networks and network connections.

Flow Control

Flow control is the process of controlling the rate at which a computer sends data. Depending on the particular protocol, both the sender and the receiver of the data (as well as any intermediate routers, bridges, or switches) might participate in the process of controlling the flow from sender to receiver. Flow control is needed because data is discarded when congestion occurs. A sender of data might be sending the data faster than the receiver can receive the data, so the receiver discards...

Flow Control Summary

One of Cisco's goals for CCNA and its other certifications is to ensure that passing means that you really understand the technology rather than simply understanding how to pass a particular exam. Focusing on understanding the concepts, as always, gives you a chance to get the exam questions correct. Table 3-6 summarizes the flow control terms and provides examples of each type. Memorizing these terms should help trigger your memory of flow-control concepts. Table 3-6 Flow-Control Methods...

Foundation Summary

The Foundation Summary is a collection of tables and figures that provide a convenient review of many key concepts in this chapter. For those of you already comfortable with the topics in this chapter, this summary could help you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your final preparation before the exam, these tables and figures will be a convenient way to review the day before the exam. Table...

Foundation Topics LAN Overview

Cisco expects CCNAs to be familiar with the three types of LANs Ethernet, Token Ring, and FDDI. There is a bias toward questions about Ethernet, which is reasonable given the installed base in the marketplace. For this reason, this chapter concentrates on Ethernet, with some comments on FDDI and Token Ring, as appropriate. Ethernet is best understood by considering the early 10Base5 and 10Base2 specifications. With these two specifications, a bus is shared among all devices on the Ethernet,...

Foundation Topics The IOS and Its User Interface

IOS, a registered trademark of Cisco Systems, is the name of the operating system found in most of Cisco's routers. The majority of Cisco routers run the IOS, with its familiar command-line interface (CLI). Also, some routing cards in other devices run IOS. For example, the Route Switch Module (RSM) card for the Catalyst 5000 series LAN switches performs routing functions and executes the IOS. Fixes and code updates to the IOS can include new features and functions. To learn more about the code...

Frame Relay Protocols

Che Carpe Montage Ligne

Frame Relay provides delivery of variable-sized data frames to multiple WAN-connected sites. Other than point-to-point links, Frame Relay is the WAN protocol most typically seen by CCNAs. This section reviews the details of how Frame Relay accomplishes its goal of delivery of frames to multiple WAN-connected sites. Frame Relay is a well-chosen name for reminding you that it most closely relates to OSI Layer 2. The term frame is generally associated with a collection of data bits that includes...

Full Duplex and Switches

Frames can be forwarded concurrently through a switch. Consider Figure 4-11, with Fred sending a frame to Wilma, and Barney sending a frame to Betty. In this figure, the switch forwards the frame coming in Port 1 out Port 3 and does the same for the frame coming in Port 2 and out Port 4. These frames also are in four different collision domains. For these reasons, no collision occurs. A four-port transparent bridge would behave the same way, but switches are optimized for concurrent frame...

Given a Network Number and a Static Subnet Mask What Are the Valid Subnet Numbers

One of the reasons you find so many different slants on IP addressing in this chapter is that the CCNA exam questions you about IP in many different ways. The question in the heading of this section is unlikely to be the exact question, however. You should expect to see something like, Which of the following are valid subnets of network X, using mask Y , followed by the suggested answers. If you can figure out all the subnets of that network, you should be able to answer the multiple-choice...

Given an IP Address and Mask What Are the Assignable IP Addresses in That Network Subnet

CCNAs deal with the question, What IP addresses are in this subnet on a regular basis. This section describes how to answer this question if you know how to derive the subnet and broadcast addresses. Simply put, the valid IP addresses that are available for assignment in a subnet are those numerically between the subnet number and the broadcast address. There is little else to be considered. Certainly, no decimal or binary algorithm needs to be considered for such a simple concept, right Table...

H gri

After the IP packet is created, routing logic is repeated by Router A, this time for the new IP packet. Router A routes the IP packet based on the IP routing table, as does Router B and then Router C. Routers B and C have no knowledge that there is an IPX packet inside the IP packet. When the packet arrives at Router D, D notices that the destination address is one of its own addresses, so it examines the data further. Upon finding the encapsulation protocol header immediately after the IP...

How Error Recovery Is Accomplished

Regardless of which protocol specification performs the error recovery, all work in basically the same way. Generically, the transmitted data is labeled or numbered. After receipt, the receiver signals back to the sender that the data was received, using the same label or number to identify the data. Figure 3-7 summarizes the operation. As Figure 3-7 illustrates, the data is numbered, as shown with the numbers 1, 2, and 3. These numbers are placed into the header used by that particular...

How the Spanning Tree Protocol Works

The Spanning-Tree Algorithm results in each bridge interface being placed into either a forwarding state or a blocking state. Interfaces in forwarding state are considered to be in the current Spanning Tree those in blocking state are not considered to be in the tree. The algorithm is elegant but basic. Figure 4-16 illustrates a network with physical redundancy, which will need to use STP. The setup in Figure 4-16 uses four switches (B1, B2, B3, and B5) and one transparent bridge. A variety of...

How to Best Use This Chapter

By taking the following steps, you can make better use of your study time Keep your notes and the answers for all your work with this book in one place, for easy reference. Take the Do I Know This Already quiz, and write down your answers. Studies show that retention is significantly increased through writing down facts and concepts, even if you never look at the information again. Use the diagram in Figure 2-1 to guide you to the next step.

Lx

Example 4-8 Single-Switch VLAN Configuration Matching Figure 4-28 switch(config) vtp transparent domain dummy switch(config) vlan 2 name VLAN2 switch(config) vtp transparent domain dummy switch(config) vlan 2 name VLAN2 Notice that some configuration seems to be missing. VLAN 1, with name VLAN1, is not configured because it is configured automatically. In fact, the name cannot be changed. Also, any ports without a specific static VLAN configuration are considered to be in VLAN1. Also, the IP...

Integrated Routing Protocols

So far, all the routing protocol functions discussed in this book fall under the classification of separate multiprotocol routing. To fully compare and contrast the meaning of this term with the alternative methods of integrated multiprotocol routing, a review of multiprotocol routing is in order. Consider Figure 6-18, which should remind you of one such concept. As discussed in Chapter 3, the router determines what type of Layer 3 packet is inside the received frame. There is a separate...

Interaction Between OSI Layers

CCNAs frequently deal with the concepts of layer interaction and encapsulation, particularly because routers build new data link headers and trailers to encapsulate the packets they route. The process of how layers interact on the same computer, as well as how the same layer processes on different computers communicate with each other, is all interrelated. The software or hardware products implementing the logic of some of the OSI protocol layers provide two general functions Each layer...

Interactions Between Adjacent Layers on the Same Computer

To provide services to the next higher layer, a layer must know about the standard interfaces defined between layers. These interfaces include definitions of what Layer N+1 must provide to Layer N to get services, as well as what information Layer N must provide back to Layer N+1. Figure 3-2 presents a graphical representation of two computers and provides an excellent backdrop for a discussion of interactions between layers on the same computer. Figure 3-2 Example for Discussion of...

Interactions Between the Same Layers on Different Computers

Layer N must interact with Layer N on another computer to successfully implement its functions. For example, the transport layer (Layer 4) can send data, but if another computer does not acknowledge that the data was received, the sender will not know when to perform error recovery. Likewise, the sending computer encodes a destination network layer address (Layer 3) in the network layer header. If the intervening routers do not cooperate by performing their network layer tasks, the packet will...

Internal Networks and Encapsulation Types

Cisco requires that CCNAs understand encapsulation, particularly with IPX. It is always Cisco's desire that the professional certifications prove that the candidate knows how to make networks that work rather than to certify individuals who are willing to memorize just for the sake of passing the test. However, IPX encapsulation is one area in which memorization is important once the base concepts are understood. Table 5-32, later in this section, lists several terms you should remember....

IP Addressing with Frame Relay Subinterfaces

Frame Relay configuration can be accomplished with or without the use of subinterfaces. If subinterfaces are not used, then all router interfaces attached to this same Frame Relay cloud should be configured with IP addresses in the same subnet. In other words, treat the Frame Relay cloud as any other multiaccess medium (such as a LAN). However, Frame Relay configuration without subinterfaces introduces some routing protocol issues when there is not a full mesh of virtual circuits (VCs) between...

IP Grouping Concepts and Subnetting

Cisco requires that CCNAs exhibit a thorough understanding of IP subnetting. Almost every organization with a network uses IP, and almost every one of these organizations uses subnetting. Subnetting is simply the process of treating subdivisions 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. The needs for subnetting are both technical and administrative, as documented in the...

IPX Addressing and Routing

Cisco requires a thorough knowledge of two protocol stacks for the CCNA exam TCP IP and Novell NetWare. Novell's NetWare protocol stack defines Internetwork Packet Exchange (IPX) as a network layer equivalent protocol, as seen in Figure 5-32. IPX will be the focus of this initial section. IPX defines the 80-bit address structure, which uses a 32-bit network part and a 48-bit node part. As with IP and AppleTalk, all interfaces attached to the same data link use addresses in the same network....

IPX Configuration

Table 5-34 IPX and IPX RIP Configuration Commands Table 5-34 IPX and IPX RIP Configuration Commands ipx network network encapsulation type Interface mode Gives detailed view of IPX parameter settings, Shows entire routing table, or one entry if debug ipx routing events 1 activity Gives messages describing each routing update Gives messages describing each SAP update Sends IPX packets to verify connectivity The first sample is a basic configuration for the network in Figure 5-37. Example 5-18,...

Ive Taken ICNDNow What

For starters, you've taken the best path to prepare yourself. But let me temper that with the fact that if you retain more than 50 percent of what you heard in class, then you are an extraordinary person That said, you need the following three strategies Strategy 1 Use this book exactly as described in the opening pages of Chapters 2 through 8, respectively. Each of the foundational chapters begins with a quiz that helps you assess what you need to study. It then directs you to the appropriate...

Ive Taken ICRCNow What

The current version of the exam more closely matches the ICND class. However, if you compared the two course books, you would find much more in common than is different. In fact, more than half of ICND is directly taken from the ICRC course. Of course, if you retain more than 50 percent of what you heard in class, then you are an extraordinary person, so you probably still need to fill in some holes in your knowledge base. For you, the following strategies will be most helpful Strategy 1 Begin...

Ive Taken the Cisco Networking Academy Courses Now What

First of all, congratulations on having the foresight to get into the Cisco Networking Academy program we need more people who can make this stuff work (Those of you who didn't take the Cisco Networking Academy track and are wondering what it's all about, check out Thankfully, the Networking Academy curriculum actually does a great job of preparing you with the skills and knowledge you need to pass the exam. Unfortunately, your study was probably spread over several semesters, and possibly over...

LAN Addressing

As a CCNA, you'll be expected to confidently understand and interpret LAN addresses. One important function of MAC addresses is to identify or address the LAN interface cards on Ethernet, Token Ring, and FDDI LANs. Frames between a pair of LAN stations use a source and destination address field to identify each other. These addresses are called unicast addresses, or individual addresses, because they identify an individual LAN interface card. (The term unicast was chosen mainly for contrast...

Topics on the Exam

The following list outlines the topics that will be the focus of the exam. These topics are shown corresponding to the chapters in which they are covered. Chapter 2, Cisco Internetwork Operating System (IOS) Fundamentals Managing configuration files Cisco Discovery Protocol (CDP) Chapter 3, OSI Reference Model & Layered Communication OSI layers, benefits of layering, interactions of OSI layers TCP IP and NetWare comparisons with OSI Connectionless and connection-oriented protocols Network...

How to Use This Book to Pass the Exam

One way to use this book is to start at the beginning and read it cover to cover. Although that certainly would help you prepare, most people would not take that much time, particularly if you already knew a lot about some of the topics in the book. The rest of you might want to consider a different strategy on how to best use this book, depending on what training you have had. This book is designed to help you get the most out of the time you take to study. The core material for the CCNA is...

LAN Framing

Figure 4-5 shows the details of LAN frames. You should remember some details about the contents of the headers and trailers for each LAN type in particular, the addresses and their location in the headers. Also, the name of the field that identifies the type of header that follows the LAN headers is important. Finally, the fact that a frame check sequence (FCS) is in the trailer for each protocol is also vital. Figure 4-5 summarizes the various header formats. The 802.3 specification limits the...

Masks and IP Address Formats

One common task that CCNAs run into is the interpretation of a network or subnet mask. This mask is used for several purposes. One key purpose is to define the number of host bits in an address. This mask also is used by computers when calculating the network or subnet number of which that address is a member. To fully appreciate what the mask is used for, you must understand the format of an IP address. Consider Figure 5-18, which shows the format of Class A, B, and C addresses when no...

MTU and Fragmentation

The maximum transmission unit (MTU) is a concept that implies the largest Layer 3 packet that can be forwarded out an interface. The maximum MTU value allowed is based on the data link protocol essentially, the maximum size of the data portion of the data link frame (where the packet is placed) is the maximum setting for the MTU on an interface. The default MTU value is 1500. If an interface's MTU is smaller than a packet that must be forwarded, fragmentation is performed by the router....

Multiple Routes to the Same Subnet

By default, the IOS supports four equal-cost routes to the same IP subnet in the routing table at the same time. This number can be changed to between 1 and 6 using the ip maximum-paths x router configuration subcommand, where x is the maximum number of routes to any subnet. As mentioned earlier, the packets are balanced on a per-destination address basis by default packets also can be balanced on a packet-by-packet basis, but at a performance penalty. The metric formula used for IGRP (and...

Network Layer Layer 3 Addressing

Cisco requires that CCNAs master the details of Layer 3 addressing, both the concepts and the particulars of IP and IPX. One key feature of network layer addresses is that they were designed to allow logical grouping of addresses. In other words, something about the numeric value of an address implies a group or set of addresses, all of which are considered to be in the same grouping. In TCP IP, this group is called a network or a subnet. In IPX, it is called a network. In AppleTalk, the...

Nonroutable Protocols

In the early and mid-1990s, one of the reasons that Cisco sold a lot of routers is that the IOS could route more Layer 3 protocols than most if not all competitors. However, some protocols are not routable. To support those, Cisco supported and evolved variations of bridging to support nonroutable protocols. What makes a protocol nonroutable Basically, a protocol stack that does not define an OSI Layer 3 equivalent, including a logical Layer 3 address structure, cannot be routed. To be fair,...

OSI Data Link Layer Functions

As a CCNA, you'll need to understand both the abstract concepts about the OSI layers and particular instances of such protocols. This section focuses on more of the abstract concepts. Chapter 4, Bridges Switches and LAN Design, and Chapter 8, WAN Protocols and Design, provide more details about particular data link protocols, as well as their configuration in the IOS. This section examines four different protocols Ethernet, Token Ring, HDLC, and Frame Relay. A generalized definition of the...

OSI Origin and Evolution

To pass the CCNA exam, you must be conversant in a protocol specification with which you are very unlikely to have any hands-on experience. The difficulty these days when using the OSI protocol specifications as a point of reference is that almost no one uses those specifications. You cannot typically walk down the hall and see a computer whose main, or even optional, networking protocols are defined by OSI. OSI is the Open Systems Interconnection reference model for communications. OSI is a...

OSI Reference Model Layered Communication

In years past, the need to understand the Open Systems Interconnection (OSI) reference model for networking grew rapidly. The U.S. government passed laws requiring vendors to support OSI software on their systems, or the government would no longer buy the systems. Several vendors even predicted that the global Internet would evolve toward using the OSI protocols instead of TCP IP. As the century turns, however, OSI has been implemented on a much smaller scale than predicted. Few vendors push...

OSI Transport Layer Functions

The transport layer (Layer 4) defines several functions. Two important features covered in this chapter are error recovery and flow control. Routers discard packets for many reasons, including bit errors, congestion that has caused a lack of buffer space, and instances in which no correct routes are known. The transport layer can provide for retransmission (error recovery) and can help avoid congestion (flow control). Transport layer protocols are typically categorized as either connectionless...

Password Recovery

Several additional concepts related to loading the IOS must be understood before password recovery can be performed. First, software called the ROM monitor (rommon) is held in ROM on all routers and actually provides the code that is first used to boot each router. rommon has a rudimentary command structure that is used as part of the password recovery process. A limited-function IOS is also held in either ROM or in additional Flash memory called bootflash in either case, the IOS in bootflash...

Qa

As mentioned in Chapter 1, All About the Cisco Certified Network Associate Certification, the questions and scenarios in this book are more difficult than what you should experience on the actual exam. The questions do not attempt to cover more breadth or depth than the exam however, they are designed to make sure that you know the answer. Rather than allowing you to derive the answer from clues hidden inside the question itself, the questions challenge your understanding and recall of the...

Questions on Scenario

1 If this is all the information that you have, what IOS do you expect will be loaded when the user reloads Nova 2 Examine the following command output in Example 2-10, taken immediately before the user is going to type the reload command. What IOS do you expect will be loaded IS-IS level-2, * - candidate default Example 2-10 show ip route on Nova (Continued) 3 Now examine the following show flash command in Example 2-11, which was issued immediately after the show ip route command in Example...

Redirect ICMP Message

ICMP redirect messages provide a very important element in routed IP networks. Many hosts are preconfigured with a default router IP address. When sending packets destined to subnets other than the one to which they are directly connected, these hosts send the packets to their default router. If there is a better local router to which the host should send the packets, an ICMP redirect can be used to tell the host to send the packets to this different router. For example, in Figure 5-14, the PC...

RIP Version

RIP Version 2, defined by RFC 1723, is simply an improved version of RIP Version 1. Many features are the same Hop count is still used for the metric, it is still a distance vector protocol, and it still uses holddown timers and route poisoning. Several features have been added, as listed in Table 6-14. This feature allows VLSM by passing the mask along with each route so that the subnet is exactly defined. Both clear text (RFC-defined) and MD5 encryption (Cisco- added feature) can be used to...

S flo S

Jane Server 3 George Gary Server 4 Steph Brice Server 5 Laurie interface serial 0.1 point-to-point ip address 168.10.12.1 255.255.255.0 ipx network 12 ipx access-group 801 in interface serial 0.2 point-to-point ip address 168.10.13.1 255.255.255.0 ipx network 13 ipx access-group 903 in interface serial 0.3 point-to-point ip address 168.10.14.1 255.255.255.0 ipx network 14 ipx access-group 903 in ip address 168.10.100.1 255.255.255.0 access-list 903 deny any 102.0000.0000.0000 1.ffff.ffff.ffff...

Scenario

Compare the following output in Example 2-7 and Example 2-8. Example 2-7 was gathered at 11 00 a.m., 30 minutes earlier than Example 2-8. What can you definitively say happened to this router during the intervening half hour Example 2-7 11 00 a.m. show running-config interface Serial0 ip address 134.141. interface Serial1 ip address 134.141. interface Ethernet0 ip address 134.141. line con 0 password cisco login line aux 0 line vty 0 4 password cisco login Example 2-8 11 30 a.m. show...

Scenario 22 Answers

The answers to the questions in Scenario 2-2 are as follows 1 The first boot system statement would be used boot system tftp c2500-js-113.bin 134.141.88.3. 2 The boot system flash command would be used. The TFTP boot would presumably fail because there is not currently a route to the subnet of which the TFTP server is a part. It is reasonable to assume that a route would not be learned 2 minutes later when the router had reloaded. So, the next boot system command (flash) would be used. 3 The...

Scenario 51 IP Addressing and Subnet Calculation

No one trusts you yet, so they will not give you any passwords to the router. Your mentor at your new company has left you at his desk while he goes to a meeting. He has left a Telnet window up, logged in to one router in user mode. In other words, you can issue only user mode commands. Assuming that you had issued the following commands (see Example 5-28), draw the most specific network diagram that you can. Write the subnet numbers used on each link onto...

Scenario 52 IP Subnet Design with a Class B Network

The topology required includes three sites, one Ethernet at each site, and point-to-point serial links for connectivity, as shown in Figure 5-44. The network may grow to need at most 100 subnets, with 200 hosts per subnet maximum. Use network 172.16.0.0. Use Table 5-46 to record your choices, or use a separate piece of paper. Scenario 5-3 IP Subnet Design with a Class C Network 331 Figure 5-44 Scenario 5-2 Network Diagram Table 5-46 Scenario 5-2 Planning Chart...

Scenario 53 IP Subnet Design with a Class C Network

Your job is to plan yet another network. The topology required includes four sites, one Ethernet at each site, and partially meshed Frame Relay for connectivity, as shown in Figure 5-45. The number of subnets will never grow. Choose a mask that will maximize the number of hosts per subnet. Use network 200.1.1.0. Use Table 5-47 to record your choices, or use a separate piece of paper. Figure 5-45 Scenario 5-3 Network Diagram Figure 5-45 Scenario 5-3 Network Diagram Location of Subnet Subnet Mask...

Scenario 55 IPX Configuration

Assume the network setup in Figure 5-47. Figure 5-47 Scenario 5-5 Network Diagram Figure 5-47 Scenario 5-5 Network Diagram Assuming the details established in Figure 5-47 for Scenario 5-5, complete or answer the following 1 Configure IPX on all three routers. Use the network numbers listed in the figure. (Do not bother with IP.) Use point-to-point subinterfaces, and use the IPX node addresses shown in the diagram on the serial interfaces. 2 You later find out that Beatrice is using NetWare's...

Scenario 71 IP Filtering Sample

Scenarios 7-1 through 7-3 all use Figure 7-13, each with a different set of requirements for filtering. In each case, configure a correct access list for the routers and enable the access list. Place the access list in the router that filters the unneeded packets as quickly as possible that is, before the packets have been sent far away from the originator. Figure 7-13 Network Diagram for IP Filtering Scenarios 7-1, 7-2, and 7-3

Scenario 72 IP Filtering Sample

Again using the network diagram in Figure 7-13, create and enable access lists for a totally different set of requirements. Place the access list in the routers to filter the unneeded packets as quickly as possible that is, before the packets have been sent far away from the originator. The filtering criteria for Scenario 7-2 is as follows 1 Hosts on the Barnaul Ethernet cannot communicate with hosts in the Gorno Ethernet. 2 Grigory and Melissa cannot communicate with hosts on the Nova...

Scenario 73 IP Filtering Sample

Again using the network diagram in Figure 7-13, create and enable access lists for a totally different set of requirements. Place the access list in the router that filters the unneeded packets as quickly as possible that is, before the packets have been sent far away from the originator. The filtering criteria for Scenario 7-3 is as follows 1 Grigory and Melissa can access any Web server in Nova. 2 Grigory and Melissa cannot access any other servers in Nova using TCP. 3 Sergei (Barnaul) can...

Scenario 74 IPX Filtering

IPX packet and SAP filtering concepts and configuration are reviewed in this scenario. Sample configurations are supplied first. Your job is to interpret the current access lists and then create new packet access lists and SAP access lists to meet some additional criteria. The details are listed after Figure 7-14 and Examples 7-17 through 7-20. Figure 7-14 Network Diagram for Scenario 7-4