A

Figure 2-16 illustrates the process of upgrading Cisco IOS Software. Figure 2-16 Complete Cisco IOS Software Upgrade Process Figure 2-16 Complete Cisco IOS Software Upgrade Process Copy startup-config to running-config The boot process follows this basic litany 1 The router performs a power-on self-test (POST) to discover and verify the hardware. 2 The router loads and runs the bootstrap code from ROM. 3 The router finds the IOS or other software and loads it. 4 The router finds the...

A a

Example 8-15 Access List at Mayberry interface serial 0 ip access-group 44 10 Describe the types of packets that this filter would discard, and specify at what point they would be discarded. 11 Does the access list in Example 8-15 stop packets from getting to Web server Governor Why or why not 12 Referring to Figure 8-8, create and enable access lists so that access to Web server Governor is allowed from hosts at any site and so that no other access to hosts in Raleigh is allowed. 13 Name all...

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...

A JL

LOBaseT, using hub, simulates single bus lOBaseT, using hub, simulates single bus The concept of cabling each device to a central hub, with that hub creating the same electrical bus as in the older types of Ethernet, was a core fact of 10BaseT Ethernet. Because hubs continued the concept and physical reality of a single electrical path that is shared by all devices, today we call this shared Ethernet All devices are sharing a single 10-Mbps bus. So, hubs solved some cabling and availability...

About the Labs in This Chapter

There are two general categories of labs in this chapter Familiarization The first two labs familiarize you with the CLI of routers and switches. They are designed for people who have not used routers and switches before, so they are very straightforward. They are also designed to be repeatable, until all the features and commands become second nature. Practice The rest of the labs are simply practice for the configuration and EXEC commands covered in a particular chapter. These labs assume...

Acknowledgments

I can write a 1000-page book, but I can't find enough words to describe the credit Chris Cleveland deserves for what is good about this book. Michael Jordan, Wayne Gretsky, Chris Cleveland a list of the absolutely best at what they do Chris, thanks for putting up with the hand-drawn figures, for meeting my schedule requirements, and for working hard during the holidays. Your ability to edit my style of writing and revising makes my job a breeze. I still refuse to write a book unless you develop...

Address Resolution Protocol

The Address Resolution Protocol (ARP) answers this question Given an IP address of another device on the same LAN, what is its MAC address ARP is needed because, to send an IP packet across some LANs, the data-link header and trailer (which encapsulate the packet) must first be created. The source MAC address in this new header is known because it is the MAC address of the sender. However, the destination MAC is not known in advance ARP is the method that IP uses to discover the destination MAC...

Answers to Scenario 102 Frame Relay Configuration

Check your IP and IPX address design against the ones chosen in Table 10-27. Of course, your choices most likely are different. However, you should have one subnet per VC when using only point-to-point subinterfaces. With the original criteria of Routers A, D, and E each using multipoint subinterfaces, these three subinterfaces should have been in the same IP subnet and IPX network. Table 10-27 lists the planned Layer 3 addresses for the configurations using multipoint among these three...

Answers to Scenario 103 Frame Relay Configuration Dissection

Figure 10-24 supplies the network diagram described in Scenario 10-3. The subinterfaces are all point-to-point, which is a clue that each VC has a subnet and IPX network associated with it. An examination of the IP addresses or IPX network numbers should have been enough for you to deduce which routers are attached to each end of each VC. Figure 10-24 Diagram of Scenario 10-3 Frame Relay Network Figure 10-24 Diagram of Scenario 10-3 Frame Relay Network Split horizon is turned off on all...

Answers to Scenario 112 IPX Configuration Answers to Task 1 for Scenario 112

Assuming the details established in Figure 11-25 for Scenario 11-2, you can find in Examples 11-24, 11-25, and 11-26 the IPX configurations on all three routers Mayberry, Mount Pilot, and Raleigh, respectively. Example 11-24 Mayberry Configuration, Scenario 11-2, Task 1 Example 11-25 Mount Pilot Configuration, Scenario 11-2, Task 1 Example 11-25 Mount Pilot Configuration, Scenario 11-2, Task 1 Example 11-26 Raleigh Configuration, Scenario 11-2, Task 1 Example 11-26 Raleigh Configuration,...

Answers to Scenario 42 LAN Switch Concepts

This scenario tests your recollection of a few of the core concepts for LAN switching. The answers are listed in succession 1 Ten collision domains exist in the network for this scenario. Routers and switches separate LANs into separate collision domains, but shared hubs do not. In this diagram, each switch port and the device(s) connected to it form the individual collision domains. 2 Two broadcast domains exist in this network. Switches and hubs do not separate the LAN segments into different...

Answers to Scenario 61 IP Addressing and Subnet Calculation

Assuming that you had issued the commands in Example 6-20, the most specific network diagram would look like Figure 6-46. Figure 6-46 Scenario 6-1 Answer Network with Router Fred Figure 6-46 Scenario 6-1 Answer Network with Router Fred 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...

Answers to Scenario 81 IP Filtering Sample

The solution to fulfilling the criteria stipulated for this access list is straightforward. Simply matching Grigory to permit his traffic and denying packets from 210.1.1.0 is all that is needed for the first two criteria. A permit all needs to be explicitly configured at the end of the list. Example 8-16 provides the solution for this scenario. The access list is enabled on Nova. The problem with list 43 is that if the link from Barnaul to Gorno goes down, and if Gorno learns a route to...

Answers to Scenario 82 IP Filtering Sample

Many solutions could fulfill the criteria stipulated for this scenario. The solutions provided in Examples 8-17 and 8-18 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 without more information about traffic loads and business needs in the network. The comments included in Examples 8-17 and 8-18 provide most of the detailed commentary. Example 8-17 Solution to Scenario 8-2...

Answers to Scenario 83 IP Filtering Sample

Many solutions could fulfill the criteria stipulated for this scenario. The solutions provided in Examples 8-19 and 8-20 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 without more information about traffic loads and business needs in the network. The comments included in Examples 8-19 and 8-20 provide most of the detailed commentary. Example 8-19 Solution to Scenario 8-3...

Answers to Scenario 91 Pointto Point Verification

Figure 9-20 is a diagram that matches the configuration. The IP and IPX addresses used on the various router interfaces were one of the tasks for this scenario. Table 9-35 is a completed version of Table 9-33, which was the blank table in which you recorded your answers for this task. Finding all the IP and IPX addresses in Examples 9-11, 9-12, and 9-13 requires some persistence. The best plan of attack is to find all the IP addresses and masks that you can, then find all the IPX network...

Answers to Task 1 for Scenario 114

Task 1 for Scenario 11-4 asks you to characterize the traffic that is discarded because of 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 confusing, given all the options. The parameters coded in the first entry in list 903 in Example 11-20 are as follows Deny Direction to throw away packets that match. 102.0000.0000.0000...

Answers to Task 1 for Scenario

Given the details in Figure 6-44 and Table 6-61 for Scenario 6-2, the subnet mask criteria are as follows 200 hosts in a subnet, maximum Static size masks used all over this network The mask must have at least eight host bits because 2' x 128 is not enough and 28 x 256 is more than enough for numbering 200 hosts in a subnet. The mask must have at least seven subnet bits, likewise, because 27 is the smallest power of 2 that is larger than 100, which is the required number of subnets. The first...

Answers to Task 2 for Scenario 112

Assuming the details established in Figure 11-25 for Scenario 11-2, the second task for Scenario 11-2 calls for additional encapsulations. Beatrice is using NetWare's Ethernet_II encapsulation, Floyd is using Ethernet_802.3, Barney is using Ethernet_802.2, and Governor is using Ethernet_SNAP. Hopefully you remembered the encapsulation names used in the IOS the names supplied in the problem statement use the NetWare names. (In real life, a simple question mark when typing the ipx network...

Answers to Task 2 for Scenario 114

Task 2 for Scenario 11-4 asks you to create IPX packet filters to meet the following criteria Clients in Nashville and Boston are not allowed access to Server 1. Clients in Charlotte are not allowed access to Server 2. Use standard access lists, if possible. Place the access lists close to the source of the packets. Assume that all access lists from Task 1 have been disabled and deleted. This can be accomplished by configuring standard IPX access lists. Because the goal is to filter packets...

Answers to Task 2 for Scenario

Based on the network design illustrated in Figure 3-23, 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....

Other Cisco Certifications

Cisco has many other certifications as well, as summarized in Table 1-2. Refer to Cisco's Web site at for the latest information. Table 1-2 Additional Cisco Certifications Table 1-2 Additional Cisco Certifications The granddaddy of them all CCIE focused on routing and switching, and is the logical conclusion after getting CCNA and then CCNP. Cisco Certified Internetworking Professional is in concept like CCNP, with a focus on service CCIE, with a focus on service provider-oriented technologies....

Answers to Task 3 for Scenario 114

Task 3 for Scenario 11-4 asks you to create SAP filters that perform the same function as described in Task 2. Task 3 suggests a very simple solution, but the simple solution works only because there are local servers in Charlotte, Nashville, and Boston. First take a look at the solution then read over some comments. Because the local server in each case will be the GNS server for the local clients, respectively, all that is needed is to stop Server 1 and Server 2 SAP information from being...

Answers to Task 3 for Scenario

Based on the network design illustrated in Figure 3-23, 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 7-2 requires that you consider 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 10.1.4.0 in its RIP update only out its subinterface 1. All other routes in Boston's routing table are learned through RIP updates from Atlanta via updates entering that same subinterface. Therefore, Boston does not advertise those routes in...

Answers to the Chapter 2 Do I Know This Already Quiz

1 What are the two different names for the router's mode of operation that, when accessed, enables you to issue commands that could be disruptive to router operations Enable and privileged mode. Both are commonly used and found in Cisco documentation. 2 What command would you use to receive command help if you knew that a show command option begins with a c but you could not recall the option You would use show c . Help would appear immediately after you typed the symbol. You would not need to...

Answers to the Chapter 3 Do I Know This Already Quiz

1 Name the seven layers of the OSI model. Application (Layer 7), presentation (Layer 6), session (Layer 5), transport (Layer 4), network (Layer 3), data link (Layer 2), and physical (Layer 1). 2 What is the main purpose(s) of Layer 3 The network layer defines logical addressing and routing as a means of delivering data across an entire network. IP and IPX are two examples of Layer 3-equivalent protocols. 3 What is the main purpose(s) of Layer 2 The data link layer defines addressing specific to...

Answers to the Chapter 5 Do I Know This Already Quiz

1 What routing protocol does a transparent bridge use to learn about Layer 3 addressing groupings None. Bridges do not use routing protocols. Transparent bridges do not care about Layer 3 address groupings. Devices on either side of a transparent bridge are in the same Layer 3 group in other words, the same IP subnet or IPX network. 2 What settings are examined by a bridge or switch to determine which should be elected as root of the spanning tree The bridge priority is examined first (the...

Answers to the Chapter 7 Do I Know This Already Quiz

1 Define what split horizon means to the contents of a routing update. Does this apply to both the distance vector algorithm and the link-state algorithm Routing updates sent out an interface do not contain routing information about subnets learned from updates entering the same interface. Split horizon is used only by distance vector routing protocols. 2 Describe the purpose and meaning of route poisoning. Route poisoning is the distance vector routing protocol feature in which a newly bad...

Approach

Retention and recall are the two features of human memory most closely related to performance on tests. This exam preparation guide focuses on increasing both retention and recall of the exam topics. The other human characteristic involved in successfully passing the exam is intelligence, but this book does not address that issue Adults' retention is typically less than that of children. For example, it is common for 4-year-olds to pick up basic language skills in a new country faster than...

Basic 1900 Switch Configuration

On the Catalyst 1900 switch, three different configuration methods exist Menu-driven interface from the console port Web-based Visual Switch Manager (VSM) IOS command-line interface (CLI) As mentioned earlier, this book focuses on using the CLI to configure the switch. Table 4-9 lists the switch commands referred to in this section. Table 4-9 Commands for Catalyst 1900 Switch Configuration Table 4-9 Commands for Catalyst 1900 Switch Configuration Sets the IP address for in-band management of...

Basic IP and Port Duplex Configuration

Two features commonly configured during switch installation are TCP IP support and the setting of duplex on key switch ports. Switches support IP, but in a different way than a router. The switch acts more like a normal IP host, with a single address mask for the switch and a default router. Each port interface does not need an IP address because the switch is not performing Layer 3 routing. In fact, if there were no need to manage the switch, IP would not be needed on the switch at all. The...

Basic RIP and IGRP Configuration

Each network command enables RIP or IGRP on a set of interfaces. You must understand the subtleties of the network command, as explained in this section. However, what enables really means in this case is not obvious from the Cisco IOS Software documentation. Also, the parameters for the network command are not intuitive to many people who are new to Cisco IOS configuration commands. Therefore, routing protocol configuration, including the network command, is a likely topic for tricky questions...

Basic VLAN Configuration

You should remember several items before you begin VLAN configuration The maximum number of VLANs is switch-dependent. The Catalyst 1900 supports 64 VLANs with a separate spanning tree per VLAN. VLAN 1 is one of the factory-default VLANs. CDP and VTP advertisements are sent on VLAN 1. Catalyst 1900 IP address is in the VLAN 1 broadcast domain. The switch must be in VTP server mode or transparent mode to create, add, or delete VLANs. Table 5-8 represents the commands covered in this section and...

Bridging and Switching

1 Name and describe two switching methods. 2 Distinguish between cut-through and store-and-forward LAN switching. 13 Describe the advantages of LAN segmentation. 14 Describe LAN segmentation using bridges. 15 Describe LAN segmentation using routers. 16 Describe LAN segmentation using switches. 17 Describe the benefits of network segmentation with bridges. 18 Describe the benefits of network segmentation with routers. 19 Describe the benefits of network segmentation with switches. So far in this...

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. Consider Figure 6-31. Class C networks 198.0.0.0 through 198.255.255.0 (they might look funny,...

CIDR Private Addressing and NAT

Connecting to the Internet using only a registered network number or several registered network numbers uses 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

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. CDP 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 particular Layer...

Cl n

Example 11-17 Albuquerque Command Output, Scenario 11-1 Albuquerque show ipx interface brief Albuquerque show cdp neighbor detail Platform cisco 2500, Capabilities Router Interface Serial0, Port ID (outgoing port) Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-AINR-L), Version Copyright 1986-1997 by Cisco Systems, Inc. Compiled Mon 29-Dec-97 18 47 by ckralik Platform cisco 2500, Capabilities Router Interface Serial1, Port ID (outgoing port) Cisco Internetwork...

Classes of Networks

RFC 790 defines the IP protocol, including three different sizes of networks. 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. Using the post office example, the network part is the ZIP code, and the host part is the street address. Just as a letter-sorting machine three states away from you cares only about the ZIP code on a letter addressed to you, a router three...

Command Syntax Conventions

The conventions used to present command syntax in this book are the same conventions used in the 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 exactly as shown. In...

Comparison of WAN Options

Networking professionals need to know about many WAN options when designing networks. Certainly, Cisco requires CCNAs to have a solid foundation of the WAN technologies described in this chapter. Cisco also expects CCNAs to be able to compare and contrast these different WAN technologies. This section summarizes many of the concepts found earlier in this chapter, with a focus on comparison. The permanent WAN connectivity options can be categorized into two main groups synchronous serial leased...

Compression

Compression can be performed on LAPB, HDLC, and PPP point-to-point serial links. The goal of compression is to reduce the number of bytes sent across the link. However, there is a price to pay for compression CPU cycles and possibly increased latency for the packets. The following list summarizes the trade-offs when you're considering whether to use compression More processing is required on the router to compress each frame, as compared with no compression. Latency per frame increases because...

Configuring Cisco IOS Software

43 Manage configuration files from the privileged exec mode. 47 Check an initial configuration using the setup command. 53 Prepare the initial configuration of your router and enable IP. 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. As mentioned in Chapter 1,...

Congestion Avoidance

Congestion avoidance is the second method of flow control covered here. The computer receiving the data notices that its buffers are filling. This causes either a separate PDU or a field in a header to be sent toward the sender, signaling the sender to stop transmitting. Figure 3-9 shows an example. Figure 3-9 Congestion-Avoidance Flow Control Sender I'm overwhelmed I'l tell him to stop I've caught up. I'll tell him to send again. Hurry up and wait is a popular expression used to describe the...

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 6-13 shows an example of connection establishment flow. Figure 6-13 TCP Connection Establishment SEQ 1450, ACK 201 SYN, ACK, DPORT 1027, SPC> RT 80 This three-way connection-establishment flow must complete before data transfer can begin. The connection...

Contents at a Glance

Chapter 1 All About the Cisco Certified Network Associate Certification 3 Chapter 2 Cisco IOS Software Fundamentals 27 Chapter 3 OSI Reference Model and Layered Communication 79 Chapter 4 LANs, Bridges, and Switches 145 Chapter 5 Intermediate LANs Spanning Tree, VLANs, and Trunking 215 Chapter 6 TCP IP and IP Routing 267 Chapter 7 Routing and Routing Protocols 407 Chapter 8 Understanding Access List Security 489 Chapter 9 WAN Protocols and Design 533 Chapter 10 Frame Relay Concepts and...

Controlling vty Access with IP Access Lists

Access into and out of the virtual terminal line (vty) ports of the Cisco IOS software can be controlled by IP access lists. (vty is used for Telnet access to and from the Cisco IOS software.) The inbound case is the more obvious case. For instance, imagine that only hosts in subnet 10.1.1.0 24 are supposed to be capable of Telnetting into any of the Cisco routers in a network. In such a case, the configuration in Example 8-14 could be used on each router to deny access from IP addresses not in...

Data Link Function 2 Addressing

Cisco requires that CCNAs master the formats and meanings of data link layer and network layer addresses. LANs need addressing because there can be many possible recipients of data that is, there could be more than two devices on the link. LANs behave much like people when you have a meeting with three or more people If you want to say something to someone in particular, you first say that person's name or at least look at him. Or, if you want to tell everyone in the meeting something, you just...

Data Link Function 3 Error Detection

Error detection discovers 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 contain an FCS field in...

DDR Legacy Concepts and Configuration

You can configure DDR in two ways DDR legacy and DDR dialer profiles. The main difference between the two is that DDR legacy associates dial details with a physical interface, whereas DDR dialer profiles disassociate the dial configuration from a physical interface, allowing a great deal of flexibility. The concepts behind DDR legacy apply to DDR dialer profiles as well, but DDR legacy is a little less detailed. Although it's not overly stated in the course, the DDR coverage in the ICND class...

DDR Step 1 Routing Packets Out the Interface to Be Dialed

Figure 9-13 provides the backdrop for these discussions. In these discussions, the SanFrancisco router dials into the main site in LosAngeles. The router must choose when to dial. The first step in this process relates to the following fact DDR does not dial until some traffic is directed (routed) out the dial interface. The router needs to route packets so that they are queued to go out the dial interface. Cisco's design for DDR defines that the router receives some user-generated traffic and,...

DDR Step 2 Determining the Subset of the Packets That Trigger the Dialing Process

Together, Steps 1 and 2 of legacy DDR logic determine when the dial is attempted. These combined steps are typically called triggering the dial. In Step 1, a packet is routed out an interface to be dialed, but that packet alone does not necessarily cause the dial to occur. The Cisco IOS Software allows the second step to define a subset of the packets routed in Step 1 to actually cause the route to dial. The logic flow is as shown in Figure 9-14. The choice in Step 2 is simply put like this Is...

DDR Step 3 Dialing Signaling

The dialing router needs additional information before the dial can occur. First, for non-ISDN interfaces, it is necessary to communicate the dial string to the external dialing device. In-band signaling (dialing) must be enabled on these interfaces using the command dialer in-band. This is not necessary on a BRI interface, because it uses the out-of-band D channel for signaling. Table 9-17 summarizes what this command implies on different interfaces. Table 9-17 Effect of the dialer in-band...

DDR Step 4 Determining When the Connection Is Terminated

The dialed link acts just like a leased line while it is up. If a particular Layer 3 protocol is enabled on the link, it can be routed across the link. Transparent (encapsulated) bridging can be used just like any other point-to-point link. Routing updates, IPX SAPs, AppleTalk ZIP, and other broadcasts are sent across the link if the broadcast keyword is coded. Most importantly, any access list used to define which packets are interesting does not filter the traffic on the interface. If packet...

Deciding What the Other Subnets

When I wrote the four-step process section for IP subnetting, I had two goals in mind. As I mentioned earlier, you need to answer subnetting questions quickly and confidently on the exam. Network engineers also think about subnetting every day, so it's great to be able to do the math in your head. So far, you have dealt with questions regarding a single subnet. You might also need to address the question What are the other valid subnets of this network The details of answering this question...

Delivering Data to the End Destination

The final router in the path also needs a list of all the address groupings, but because the destination is on the same LAN as the router, this final router needs to look at the entire address. When the packet arrives at a router sharing a data link with the true destination, the router and the destination of the packet are in the same L3 grouping. That final router can forward the data directly to the destination. As usual, a new data-link header and trailer are created before a frame (which...

Distance Vector Advanced Concepts

Two general categories of topics are explained in the rest of this section. First, when multiple physical paths exist in a network, multiple routes to the same network can exist. If that occurs, the metrics could tie, so which one do you use Well, it depends, so we will take a closer look. The second category of topics relates to loop avoidance. Just like Spanning-Tree Protocol avoids loops in a switched or bridged LAN, IP routing protocols avoid loops in the routed IP network. Distance vector...

Distance Vector Routing Protocol Behavior

CCNAs deal with routing problems on a daily basis. Some of these problems are the result of the logic behind distance vector routing protocols. Understanding 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 Routers add directly connected...

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 three smaller four-question quizlets, which correspond to the three major topic headings in the chapter. Figure 2-1 outlines suggestions on how to spend your time in this chapter...

EIGRP and Balanced Hybrid Protocols

A second type of routing protocol is the balanced hybrid protocol. Balanced hybrid is a term created by Cisco to describe the inner workings of EIGRP, which uses the Diffusing Update Algorithm (DUAL) to calculate routes. A balanced hybrid protocol exchanges more topology information than a distance vector routing protocol, but it does not require full topology or the computation-intensive Dijkstra algorithm to compute loop-free routes. Enhanced IGRP (EIGRP) is a balanced hybrid routing...

Electing the Root Discovering Root Ports and Designated Ports

Each bridge begins by claiming to be the root bridge by sending STP messages. STP defines these messages used to exchange information with other bridges, which are called bridge protocol data units (BPDUs). Each bridge begins by sending a BPDU stating the following The root bridge's bridge ID At the beginning of the process, each bridge claims to be root, so this value is the same as the bridge ID of this bridge. An administratively set priority This is the priority of the root bridge. At the...

Equipment List

You will of course need some equipment in order to do the labs. Because different people might buy different equipment, this list describes the gear generically Routers (you need two) Each router needs IP IPX enabled in Cisco IOS Software, as well as one Ethernet and one Serial interface. The serial interface can be a synchronous interface or an async sync interface. These are priced around 500 to 600 on eBay. 1900 series switch (you need one or two) One lab exercise requires one switch, and...

Error Detection and Looped Link Detection

Error detection and looped link detection are two key features of PPP. Looped link detection allows for faster convergence when a link fails because it is looped. (Links are typically looped for testing purposes.) When this occurs, a router continues to receive the looped Cisco proprietary keepalive messages, so the router might not think that the link has failed. For example, the absence of routing updates from a neighbor for a certain length of time is used to drive convergence. Waiting on...

Error Recovery

Cisco expects CCNAs to be able to distinguish between error detection and error recovery. Any header or trailer with a frame check sequence (FCS) or similar field can be used to detect bit errors in the PDU. The FCS uses some magic math against the contents of the frame, with the result recorded in the FCS field. If the receiving device repeats the same math but gets a different value than what is in the FCS field, there were bit errors in transmission. Error detection uses the FCS to detect...

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. If you remember error recovery from Chapter 3, OSI Reference Model and Layered Communication,...

Exam Topics in This Chapter

42 Examine router elements (RAM, ROM, CDP, show). 43 Manage configuration files from the privileged exec mode. 44 Control router passwords, identification, and banner. 45 Identify the main Cisco IOS Software commands for router startup. 46 Log in to a router in both user and privileged modes. 47 Check an initial configuration using the setup command. 48 Use the context-sensitive help facility. 49 Use the command history and editing features. 50 List the commands to load Cisco IOS Software from...

Examination of RIP and IGRP debug and show Commands

Figure 7-10 Sample Three-Router Network with Subnet 10.1.2.0 Failing Figure 7-10 Sample Three-Router Network with Subnet 10.1.2.0 Failing Example 7-4 RIP Configuration and debugs on Albuquerque received v1 update from 10.1.6.253 on Seriall 10.1.3.0 in 1 hops 10.1.2.0 in 2 hops 10.1.5.0 in 1 hops sending v1 update to 255.255.255.255 via Serial0 (10 (POINT NUMBER 1) subnet subnet subnet sending v1 subnet subnet subnet sending v1 subnet subnet subnet subnet subnet update to 255.255.255.255 via...

Example Configuration Process

Example 2-1 illustrates how the console password is defined provides banner, host name, prompt, and interface descriptions and shows the finished configuration. The lines beginning with are comment lines that highlight significant processes or command lines within the example. The show running-config command output also includes comment lines with just a to make the output more readable many comment lines in the examples in this book were added to explain the meaning of the configuration. You...

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...

Extended IP Access Lists Example

The first example is basic in order to cover the statements syntax. In this case, Bob is denied access to all FTP servers on R1's Ethernet, and Larry is denied access to Server1's Web server. Figure 8-6 is a reminder of the network topology. In Example 8-6, an access list is created on R1. Example 8-6 shows the configuration on R1. Figure 8-6 Network Diagram for Extended Access List Example 1 Figure 8-6 Network Diagram for Extended Access List Example 1 Example 8-6 R1's Extended Access List...

Fast Ethernet and Gigabit Ethernet

Fast Ethernet and Gigabit Ethernet provide faster Ethernet options. Both have gained widespread acceptance in networks today, with Fast Ethernet most likely being used to the desktop and Gigabit Ethernet being used between networking devices or to servers. Fast Ethernet retains many familiar features of 10-Mbps Ethernet variants. The age-old CSMA CD logic still exists, but it can be disabled for full-duplex point-to-point topologies in which no collisions can occur. A variety of cabling options...

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 prevents unnecessary congestion by attempting to send data at a rate that the network can currently accomodate. A sender of data might be sending the data faster than the...

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. The...

Foundation Topics Spanning Tree Protocol

1 Describe the operation of the Spanning Tree Protocol and its benefits. In the absence of STP, frames would loop for an indefinite period of time in networks with physically redundant links. STP blocks some ports so that only one active path exists between any pair of LAN segments (collision domains). The result of STP is both good and bad Frames do not loop infinitely, which makes the LAN usable, which is good. However, the network does not actively take advantage of some of the redundant...

Foundation Topics Tcpip Protocols

21 Identify the functions of the TCP IP network-layer protocols. 22 Identify the functions performed by ICMP. 26 Define flow control and describe the three basic methods used in networking. CCNAs work with multiple protocols on a daily basis none of these is more important than TCP IP. This section examines the TCP, UDP, ICMP, and ARP protocols in detail. TCP and UDP are the two transport layer (Layer 4) protocols most often used by applications in a TCP IP network. ICMP and ARP are actually...

Foundation Topics The Cisco IOS Software Command Line Interface

42 Examine router elements (RAM, ROM, CDP, show). 44 Control router passwords, identification, and banner. 45 Identify the main Cisco IOS Software commands for router startup. 46 Log in to a router in both user and privileged modes. 48 Use the context-sensitive help facility. 49 Use the command history and editing features. The majority of Cisco routers run Cisco IOS Software, with its familiar command-line interface (CLI). Some routing cards in other devices also run Cisco IOS Software. For...

HDLC and PPP Configuration

One common task for CCNAs is to enable an appropriate point-to-point data-link protocol. The configuration is straightforward, with LAPB being the exception. Be sure to configure the same WAN data-link protocol on each end of the serial link. Otherwise, the routers will misinterpret the incoming frames, and the link will not work. Tables 9-4 and 9-5 summarize the configuration commands and the show and debug commands used for HDLC and PPP configuration. Table 9-4 PPP and HDLC Configuration...

How Spanning Tree Works

The STP algorithm creates a spanning tree of interfaces that either forward or block. STP actually places interfaces into forwarding state by default, if an interface has no reason to be in forwarding state, it is placed into a blocking state. In other words, STP simply picks which interfaces should forward. So, how does STP choose whether to put an interface into forwarding state Well, it uses three criteria STP elects a root bridge. All interfaces on the root bridge are in forwarding state....

How This Book Is Organized

This book contains 10 core chapters Chapters 2 through 11. Each chapter covers a subset of the topics on the exam. Along with these core chapters, three other chapters help you succeed on the CCNA exam. Chapter 1 helps you understand how to use this book to efficiently and effectively study for the CCNA exam. Chapter 12 is full of lab scenarios that force you to think about all the topics in the book, which helps you with final preparation. And, if you can get access to some lab gear, read...

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 3-1 to guide you to the next step.

ICMP Echo Request and Echo Reply

The ICMP Echo Request and Echo Reply messages are sent and received by the ping command. In fact, when people say that they sent a ping packet, they really mean that they sent an ICMP Echo Request. These two messages are very self-explanatory. The Echo Request simply means that the host to which it is addressed should reply to the packet. The Echo Reply is the ICMP message type that should be used in the reply. The Echo Request includes some data that can be specified by the ping command...

IGRP Configuration

You configure IGRP just like RIP, except that the router igrp command has an additional parameter the AS number. All that is needed is for all routers to use the same process-id in order for IGRP to work. In Example 7-3, a complete sample IGRP configuration causes the router to advertise all connected subnets, to listen on all interfaces for IGRP updates, and to advertise on all interfaces. Example 7-3 Sample IGRP Configuration and show ip route Command Output interface ethernet 0 ip address...

IGRP Metrics

This metric is calculated as a function of bandwidth, delay, load, and reliability. By default, only bandwidth and delay are considered the other parameters are considered only if they are enabled via configuration. Delay and bandwidth are not measured values but are set via the delay and bandwidth interface subcommands. (The same formula is used to calculate the metric for EIGRP, but with a scaling factor so that the actual metric values are larger, allowing more...

Im New to Internetworking with Cisco I Will Not Be Taking the ICND Course and I Bought the Interconnecting Cisco

If you have no networking experience at all, start with the ICND book. The CCNA exam lists ICND as the main prerequisite course before taking the exam. The Cisco Press ICND book contains the actual ICND course materials, handed over by Cisco to Cisco Press, and then converted into book format. The same figures used in the presentations by instructors are used as the figures in the book, with explanations matching what a senior instructor might say when teaching the course. So, if you use one...

Info

Source Destination Source Destination 10.1.1.1 170.1.1.1 200.1.1.1 170.1.1.1 Source Destination Source Destination 170.1.1.1 10.1.1.1 170.1.1.1 200.1.1.1 NAT also can be used when the private organization is not using private addressing but is instead using a network number registered to another company. (A client company of mine originally had done just that ironically, the company was using a network number registered to Cabletron, which my client saw used in a presentation by an ex-Cabletron...

Intermediate LANs Spanning Tree VLANs and Trunking

Engineers need a basic knowledge of LANs and Ethernet to plan, design, build, and troubleshoot a small site with a single LAN. However, when building a larger intermediate-sized LAN, several additional LAN features must be understood. You can install LANs that use VLANs and multiple switches without understanding a lot of what is in this chapter, but if you want the network to work well, you should understand these topics. Most LANs with multiple interconnected switches have redundant Ethernets...

Internal Switching Paths

The internal processing on a switch can decrease latency for frames. Transparent bridges use store-and-forward processing, which means that the entire frame is received before the first bit of the frame is forwarded. Switches can use store-and-forward processing as well as cut-through processing logic. With cut-through processing, the first bits of the frame are sent out the outbound port before the last bit of the incoming frame is received instead of waiting for the entire frame to be...

IP Addressing with Frame Relay Subinterfaces

Frame Relay behaves like a WAN in some ways and more like a LAN in other ways. To overcome some routing protocol issues that will be discussed in Chapter 7, Routing and Routing Protocols, and Chapter 10, Frame Relay Concepts and Configuration, Cisco provides three different ways to configure IP addresses on Frame Relay serial interfaces 1 Configure the IP addresses on the normal physical interface, just like for other interfaces. By doing so, all routers on the Frame Relay network are in the...

IP Configuration

You can easily configure a Cisco router to forward IP traffic when you know the details covered in this chapter so far. Tables 6-48 and 6-49 summarize many of the most common commands used for IP configuration and verification. Two sample network configurations, with both configuration and exec command output, follow. The Cisco IOS documentation is an excellent reference for additional IP commands the Cisco Press book Interconnecting Cisco Network Devices is an excellent reference, particularly...

IP Naming Commands and Telnet

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. The IOS can use statically configured names as well as refer to one or more DNSs. Example 6-13 shows some names statically configured, with configuration pointing to two different DNSs....

ISDN Channels

The IOS documentation focuses on two types of ISDN interfaces Basic Rate Interface (BRI) and Primary Rate Interface (PRI). Both BRI and PRI provide multiple digital bearer channels over which temporary connections can be made and data can be sent. The result is concurrent digital dial access to multiple sites. Table 9-9 summarizes the features of BRI and PRI. Bearer channels (B channels) are used to transport data. B channels are called bearer channels because they bear the burden of...

ISDN Configuration

Examples 9-8 and 9-9 show the DDR configuration for the network shown in Figure 9-15. ISDN configuration details have been added. The text following these two examples describes the ISDN commands shown. Example 9-8 Completed SanFrancisco Configuration ip route 172.16.3.0 255.255.255.0 172.16.2.1 ip route 172.16.4.0 255.255.255.0 172.16.2.3 Added usernames for CHAP support username LosAngeles password Clark username GothamCity password Bruce access-list 101 permit tcp any host 172.16.3.1 eq 80...

ISDN Protocols and Design

33 Identify ISDN protocols, function groups, reference points, and channels. Integrated Services Digital Network (ISDN) provides switched (dialed) digital WAN services in increments of 64 kbps. The phone companies of the world created ISDN as a key building block for digital services of the future things such as faster computing devices that can take advantage of speeds greater than 9600 bps. Another possibility is digital phones. And because ISDN uses 64 kbps bearer channels, and the phone...

Issues When Multiple Routes to the Same Subnet Exist

A router might learn one route and then learn a better route. Of course, the better route should replace the higher-metric route when this happens. Figure 7-4 outlines just such a case. Table 7-6 shows Router B's routing table when only one route to 162.11.10.0 is known, before the serial link between B and C comes up. Table 7-7 shows Router B's routing table after the link between B and C comes up, learning about another route to that same subnet. Figure 7-4 Routers A and C Advertising to...

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, you are an extraordinary person That said, you need the following two strategies Strategy 1 Begin by using the Book 2 approach because you already have learned a lot about the topics on the exam. Each of the core chapters of the book, Chapters 2 through 11, begins with a quiz that helps you assess what you need to study. The...

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 can 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...

Lab 1 Hints

I searched for console connection on www.cisco.com, and I found this pointer that might be helpful If you do everything right but forget to press Enter, the router or switch will not write anything to the screen. You will not hurt anything by pressing Enter too many times Always try a different console cable and connector, make sure the cables are connected well, and make sure the cable is plugged into the console port, not the auxiliary port. Use the disable and enable commands to move back...

Lab 1 Objectives

When finished with this lab, you will be able to do the following Log in to a Cisco router via the console port Configure the passwords needed to log in via the console port and to enter privileged mode Get help via the router user interface Get help in EXEC and configuration modes Use several basic switch EXEC and configuration mode commands easily Navigate the different modes of the Cisco 1900 series switch CLI This lab is intended to force you to try out several features of the CLI. You can,...

Lab 1 Stepby Step Instructions

Step 1 Connect the console cable between your PC's COM1 port and a router's console port. Step 2 Bring up your favorite terminal emulator program. If you do not have a favorite, use HyperTerminal, which comes with Microsoft operating systems. Select Start, Programs, Accessories, Communications, HyperTerminal. Step 3 Ignore attempts to make you configure a phone number, but configure terminal characteristics of 9600 bps, 8 bits byte, no parity, and 1 start stop bit. This combination is often...