Overview of a Sample Tcpip Network
TCP IP encompasses a lot of smaller protocols in fact, the name itself is a combination of two of the most popular of these many protocols, the Transmission Control Protocol and the Internet Protocol. The best way to get a sense of how some of these varied TCP IP protocols work together is to examine a simple TCP IP network with some simple applications. After that, we will look at each protocol more closely. The sample network consists of two PCs, labeled Hannah and Jessie. Hannah uses an...
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...
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 that correspond to the three major topic headings in this chapter. Figure 8-1 outlines suggestions on how to spend your time in this chapter...
Scenario 101 Frame Relay Verification
Use Examples 10-19 through 10-22 when completing the exercises and answering the questions that follow. Example 10-19 Atlanta Command Output, Scenario 10-1 Serial0 is up, line protocol is up Hardware is HD64570 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255 255, load 1 255 Encapsulation FRAME-RELAY, loopback not set, keepalive set (10 sec) LMI enq sent 32, LMI stat recvd 32, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 1023 LMI type is CISCO...
Scenario 42 LAN Switch Concepts
In this scenario, you will answer some questions about a simple network diagram. Figure 4-21 depicts the network. Answer the questions that follow the diagram. Figure 4-21 Scenario 4-2 Basic LAN Switch Concepts Figure 4-21 Scenario 4-2 Basic LAN Switch Concepts 1 How many collision domains exist in this network 2 How many broadcast domains exist in this network 3 Assuming that all cards, switches, and router interfaces are 10 100 cards, how many ports total on each switch could run full duplex...
Solutions to Scenario 122 Part B Configuration
Examples 12-7, 12-8, and 12-9 show the configurations for tasks 1, 2, and 3. ip address 168.11.123.201 255.255.255.192 ip address 168.11.11.101 255.255.255.192 ipx network 111 encapsulation novell-ether secondary ip address 168.11.123.202 255.255.255.192 ip address 168.11.12.102 255.255.255.192 ipx network 120 encapsulation sap ipx network 121 encapsulation snap secondary interface serial0 encapsulation frame-relay ip address 168.11.123.203 ipx network 123 frame-relay interface-dlci Example...
RIP1 and IGRP No Subnet Masks
RIP-1 and IGRP do not transmit the subnet mask in the routing updates, as seen in the debug output in earlier examples. Cisco expects you to be able to explain why routing protocols that do not transmit a mask can have problems in some networks. This section explains these problems, which all originate from the same root cause. NOTE Routers must assume the subnet mask that should be used with a subnet number listed in a routing update. Routing protocols that do not transmit masks, such as RIP...
Frame Relay Configuration
30 List commands to configure Frame Relay LMIs, maps, and subinterfaces. 31 List commands to monitor Frame Relay operation in the router. This chapter describes Frame Relay concepts. For example, three LMI types and two encapsulation types are available. Depending on the placement of your VCs, you might want to use one subnet for the whole Frame Relay network, one subnet per VC, or a mixture of the two. You might need to configure static mapping of IP addresses and their corresponding DLCIs....
Dialon Demand Routing
As a CCNA, you'll need to understand both ISDN configuration and the related DDR configuration that causes the Cisco IOS Software to use the BRI interface. You must understand DDR configuration and concepts before the ISDN configuration topics will make complete sense. ISDN configuration can be very brief, whereas DDR can become quite involved. In this section, DDR is explained first, and then ISDN configuration is discussed. DDR defines the logic behind when a router chooses to dial another...
Step 2 Create the Chart to Be Used in Steps 3 and
Step 2 simply introduces you to a tool that you can use to teach yourself how to quickly derive the subnet number and first valid address (Step 3) and the broadcast address and last valid address (Step 4). This tool, which is a chart that you will complete, organizes the given information (address and mask) along with the information that you need to derive. This tool will help you learn to perform subnetting with no binary math, which you will need to do in most networking jobs.When you become...
Foundation Summary
The Foundation Summary is a collection of tables and figures that provide a convenient review of many key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary will help you recall a few details. If you just read this chapter, this review will help solidify some key facts. If you are doing your final preparation before the exam, these tables and figures are a convenient way to review the day before the exam. Figure 10-20 shows some connectivity...
Scenario 73 IP Addressing and Subnet Derivation
Complete the tasks and answer the questions following the upcoming figures and examples. Figure 7-16 shows the network diagram for Scenario 7-3, and Examples 7-22, 7-23, and 7-24 contain show command output from the three routers. Use Table 7-29 to record the subnet numbers and broadcast addresses as directed in the upcoming tasks. Figure 7-16 Scenario 7-3 Network Diagram Table 7-29 Subnets and Broadcast Addresses Table 7-29 Subnets and Broadcast Addresses Table 7-29 Subnets and Broadcast...
Access to the CLI
Cisco uses the acronym CLI to refer to the terminal user command-line interface to the IOS. The term CLI implies that the user is typing commands at a terminal, a terminal emulator, or a Telnet connection. Although you can pass the CCNA exam without ever having used the CLI, actually using the CLI will greatly enhance your chances. To access the CLI, use one of three methods, as illustrated in Figure 2-2. Figure 2-2 CLI Access You access the router through the console, through a dialup device...
Answers to the Chapter 4 QA Section
1 What do the letters MAC stand for What other terms have you heard to describe the same or similar concept Media Access Control (MAC). Many terms are used to describe a MAC address NIC, LAN, hardware, BIA, universally administered address (UAA), locally administered address (LAA), Ethernet, Token Ring, FDDI, card, wire, and real are all terms used to describe this same address in different instances. 2 Name two benefits of LAN segmentation using transparent bridges. The main benefits are...
LAN Switching
An Ethernet switch uses the same logic as a transparent bridge. However, switches perform more functions, have more features, and have more physical ports. Switches use hardware to learn addresses and to make forwarding and filtering decisions. Bridges use software running on general-purpose processors, so they tend to run much more slowly than switches. The reason behind this difference is simply the time frame in which each technology was developed Switches came later and took advantage of...
Upgrading an IOS Image into Flash Memory
IOS files typically are stored in Flash memory. Flash memory is rewriteable, permanent storage, which is ideal for storing files that need to be retained when the router loses power. Also, because there are no moving parts, there is a smaller chance of failure as compared with disk drives, which provides better availability. As you will read soon, IOS can be placed on an external TFTP server, but using an external server typically is done for testing in production, practically every Cisco...
Network Layer Concerns with Frame Relay
Most of the important Frame Relay concepts have been covered. First, the routers (DTEs) connect to the Frame Relay switches (DCEs) over an access link, which is a leased line between the router and the switch. The LMI protocol is used to manage the access link, and the LMI type must match between the router and the local switch. The routers agree to the style of encapsulation used. The single DLCI field in the Frame Relay header identifies the VC used to deliver the frame. The DLCI is used like...
Fully Meshed Network with One IP SubnetIPX Network
The network engineer designed a fully-meshed network for the first example. This first sample network, based on the environment depicted in Figure 10-12, does not use subinterfaces, but rather includes all Frame Relay configuration under the physical interface. Multipoint subinterfaces could have been used instead. Examples 10-1, 10-2, and 10-3 show the configuration for the network shown in Figure 10-15. Figure 10-15 Full Mesh with IP and IPX Addresses 199.1.1.2 199.1.1.3 199.0020.BBBB.BBBBW...
ISDN Function Groups and Reference Points
Many people are confused about the ISDN terms reference point and function group. One key reason for the confusion is that only some function groups and therefore some reference points are used in a single topology. Cisco expects CCNAs to be familiar with all function groups and reference points. In an effort to clear up these two topics, consider the following inexact but more-familiar definitions of the two Function group A set of functions implemented by a device and software Reference point...
Time Exceeded ICMP Message
The ICMP Time Exceeded message notifies a host when a packet that it sent has been discarded because it was out of time. Packets are not actually timed, but to prevent packets from being forwarded forever when there is a routing loop, each IP header uses a Time to Live (TTL) field. Routers decrement TTL by one every time they forward a packet if a router decrements TTL to zero, it throws away the packet. This prevents packets from rotating forever. Figure 6-20 shows the basic process. TTL minus...
Binary View of Subnetting
Computers, especially routers, do not think about IP addresses in terms of conventions. They think in terms of 32-bit binary numbers, which is fine because, technically, that's what IP addresses really are. Also, computers use a mask to define the structure of these binary IP addresses. A full understanding of what that means is not difficult in fact, if you understood the last section of the book, you already understand the structure of an IP address. However, getting accustomed to doing the...
Scenario 91 Pointto Point Verification
Use Examples 9-11, 9-12, and 9-13 when completing the exercises and answering the questions that follow. Example 9-11 Albuquerque Command Output for Scenario 9-1 Codes C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U -...
LMI and Encapsulation Types
When you're first learning about Frame Relay, it's often easy to confuse the LMI and the encapsulation used with Frame Relay, but Cisco expects CCNAs to master the differences. The LMI is a definition of the messages used between the DTE (for example, a router) and the DCE (for example, the Frame Relay switch owned by the service provider). The encapsulation defines the headers used by a DTE in order to communicate some information to the DTE on the other end of a VC. The switch and its...
Answers to Scenario 41 LAN Switch Configuration
This scenario should have forced you to perform basic LAN configuration. Figure 4-22 lists the port numbers and MAC addresses used for the solution. Example 4-7 lists the output from actually performing these steps sequentially on a 1900 series switch. An explanation of the steps follows the example. Example 4-7 Scenario 4-1 Configuration and show Commands delete nvram This command resets the switch with factory defaults. All system parameters will revert to their default factory settings. All...
Step 4 Derive the Subnet Broadcast Address and the Last Valid IP Address
NOTE Reminder If you want to focus on the easy example and then come back and reread this section when you are comfortable with the easy one, continue to avoid reading the shaded areas of this section. Step 4 completes the process using the subnet chart to answer the most typical subnetting questions. You need to know how to calculate the subnet broadcast address as well as the last IP address in the subnet, which is one less than the broadcast address. After you calculate the broadcast...
Troubleshooting Routing and Routing Protocols
Cisco would like all its certification exams CCNA included to prove that the test taker can build and troubleshoot live networks. Some people work with Cisco routers daily. Others' job function does not allow frequent access to routers. If the latter description applies to you, you might be trying to pass this certification so that you can move into jobs that involve routers and switches. Regardless, this section gives you some final insights into some tricky problems with routing protocols....
Answers to the Chapter 7 QA Section
1 What type of routing protocol algorithm uses a hold-down timer What is its purpose Distance vector. Holddown helps prevent counting-to-infinity problems. Holddown is explained in detail in the section Distance Vector Routing Protocols in Chapter 6, TCP IP and IP Routing. After learning that a route has failed, a router waits for a hold-down timer before believing any new information about the route. 2 Define what split horizon means to the contents of a routing update. Does this apply to both...
Answers to Scenario 51 LAN Switch Configuration
The first task required you to assign port numbers to the diagram. The task ends up being much more tricky than just picking the ports. 1900 series switches have two 100-Mbps ports, and because ISL and 802.1Q trunking require at least 100-Mbps Ethernet, these two ports are the only ports over which trunking can be used. So, trunking between R1 and SW1 requires one 100-Mbps port, leaving only one additional trunk port on SW1 for connection to the other two switches. In this scenario, the problem...
IP Grouping Concepts and Subnetting
The creators of the Internet realized the impracticality of the original network-numbering conventions early on. Computing history shows many examples of people being unable to conceive the idea that computing technology would grow as fast as it has. Needless to say, the Internet would have run out of Class A, B, and C networks long ago if additional addressing features had not been created. Subnetting provided the first significant addressing feature that conserved the global IP address space....
ISDN Protocols
Coverage of ISDN protocols and their specifications on the CCNA exam poses a particularly difficult problem for the CCNA candidate. The ITU defines the most well-known specifications for ISDN, but there are far more specifications than anyone could memorize. The problem is choosing what to memorize and what to ignore. My personal philosophy is that standards information is best kept in a book rather than in my own memory. With Cisco's emphasis on proving your hands-on skills using the CCNA and...
How VTP Works
VTP advertisements are flooded throughout the management domain every 5 minutes, or whenever there is a change in VLAN configurations. Included in a VTP advertisement is a configuration revision number, as well as VLAN names and numbers, and information about which switches have ports assigned to each VLAN. By configuring the details on one server and propagating the information through advertisements, all switches know the names and numbers of all VLANs. One of the most important components of...
Extended IP Access Lists Example
Figure 8-7 shows the network for another example of extended IP access lists. The filtering criteria for this extended access list example are more complicated The Web server (Daffy) is available to all users. UDP-based clients and servers on Bugs are unavailable to hosts whose IP addresses are in the upper half of the valid IP addresses in each subnet. (The subnet mask used is 255.255.255.0.) Packets between hosts on the Yosemite Ethernet and the Seville Ethernet are allowed only if packets...
IP Addressing and Subnetting
Engineers use IP addressing terminology in many different ways and sometimes people use the terms to mean slightly different things. Table 6-7 lists the IP terms used in the upcoming sections, giving an exact definition. Feel free to refer to this table as you read. A 32-bit number, usually written in dotted-decimal form, that uniquely identifies an interface of some computer. A group of hosts, all of which have an identical beginning portion A 32-bit number, usually written in dotted-decimal...
Virtual LANs
4 Describe the benefits of virtual LANs. This chapter focuses on some of the additional features that are required to implement intermediate-sized LANs. Chapter 4, LANs, Bridges, and Switches, focused on the basics of LANs. Frankly, though you probably could have bought several Cisco switches, cabled them together, and made them work with absolutely no configuration required, ignoring everything we have covered so far. Why is that Well, Cisco switches with 10 100 ports autonegotiate by default....
CLI Help Features
If you printed the IOS Command Reference documents, you would end up with a stack of paper several feet tall. No one should expect to memorize all the commands and no one does in real life, either. Several very easy, convenient tools can be used to help you remember commands and then also save you time typing. As you progress through your Cisco certifications, the exam will cover progressively more commands. However, the only Cisco exam that covers the methods of getting command help is the...
DLCI Addressing Details
So far, you know some basic information about Frame Relay. First, the routers (DTEs) connect to the Frame Relay switches (DCEs) over an access link, which is a leased line between the router and the switch. The logical path between a pair of DTEs is called a virtual circuit (VC). Permanent virtual circuits (PVCs) are typically used, and the data-link connection identifier (DLCI) is used to address or identify each individual PVC. The LMI protocol is used to manage the access link, and the LMI...
Foundation Topics Standard IP Access Lists
35 Configure standard access lists to filter IP traffic. 37 Monitor and verify selected access list operations on the router. IP access lists cause a router to discard some packets based on criteria defined by the network engineer. The goal of these filters is to prevent unwanted traffic in the network whether to prevent hackers from penetrating the network, or just to prevent employees from using systems that they should not be using. Access lists should simply be part of an organization's...
Answers to the Chapter 8 Do I Know This Already Quiz
1 Configure a numbered IP access list that stops packets from subnet 134.141.7.0 255.255.255.0 from exiting serial 0 on a router. Allow all other packets. access-list 4 deny 134.141.7.0 0.0.0.255 access-list 4 permit any interface serial 0 ip access-group 4 The first access-list statement denies packets from that subnet. The other statement is needed because the default action to deny packets is not explicitly matched in an access-list statement. 2 How would a user who does not have the enable...
Foundation Topics Novell IPX Concepts
25 List the required IPX address and encapsulation type. 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. Novell also specifies several routing protocols, with Novell RIP being the one covered on the CCNA exam. NetWare also defines the Service Advertisement Protocol (SAP), which is used by servers and routers to exchange...
Partially Meshed Network with One IP SubnetIPX Network Per VC
The second sample network, based on the environment shown in Figure 10-18, uses point-to-point subinterfaces. Examples 10-8 through 10-11 show the configuration for this network. The command prompts are included in the first example because they change when you're configuring subinterfaces. Figure 10-18 Partial Mesh with IP and IPX Addresses Figure 10-18 Partial Mesh with IP and IPX Addresses Atlanta(config) ipx routing 0200.aaaa.aaaa Atlanta(config) interface serial0 Atlanta(config-if)...
Partially Meshed Network with Some Fully Meshed Parts
Frame Relay networks built by CCNAs usually include both point-to-point and multipoint subinterfaces. This last sample network (based on the environment shown in Figure 10-19) uses both types of subinterfaces. Examples 10-13 through 10-17 show the configuration for this network. Table 10-14 summarizes the addresses and subinterfaces used. Figure 10-19 Hybrid of Full and Partial Mesh 1 '' uLwi auo f uLwi aut ULWI aua f Table 10-14 IP and IPX Addresses with Point-to-Point and Multipoint...
Whats on the CCNA Exam
Every test taker would like to know exactly what is on the CCNA exam as well as the other Cisco certification exams. Well, to be honest, exactly what is on the exam is a very closely guarded secret. Only those who write the questions for Cisco and who have access to the entire question database truly know what is really on the exam. Cisco makes fairly general CCNA exam content available to the public at the Web site In fact, this direct quote from the Cisco Web site summarizes the exam CCNA...
Answers to the Chapter 2 QA Section
1 What are the two names for the router's mode of operation that, when accessed, enables you to issue commands that could be disruptive to router operations Enable mode and privileged mode. Both modes are commonly used and found in Cisco documentation. 2 What are three methods of logging on to a router Console, auxiliary port, and Telnet. All three cause the user to enter user EXEC mode. 3 What is the name of the user interface mode of operation used when you cannot issue disruptive commands 4...
Answers to the Chapter 5 QA Section
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 3 QA Section
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). Some mnemonics to help you recall the names of the layers are All People Seem To Need Data Processing (Layer 7 to 1), Please Do Not Take Sausage Pizzas Away (Layer 1 to 7), and the ever-popular Pew Dead Ninja Turtles Smell Particularly Awful (Layer 1 to 7). 2 What is the main purpose(s) of Layer 7 Layer 7...
Answers to the Chapter 6 QA Section
1 What do TCP, UDP, IP, and ICMP stand for Which protocol is considered to be Layer 3-equivalent when comparing TCP IP to the OSI protocols Transmission Control Protocol, User Datagram Protocol, Internet Protocol, and Internet Control Message Protocol. Both TCP and UDP are Layer 4 protocols. ICMP is considered a Layer 3 protocol because it is used for control and management of IP. IP is the core part of the network layer of TCP IP. 2 Name the parts of an IP address. Network, subnet, and host...
Step 3 Derive the Subnet Number and the First Valid IP Address
NOTE Before beginning the explanations in Steps 3 and 4 of this process, you might want to choose to not read parts of this section. If you are not yet comfortable with subnetting when easy masks are used, you might benefit from focusing on the example that covers the easy masks used and ignoring the hard example. Then, when you are comfortable with the easy ones, reread all of Steps 3 and 4. To help you focus on the easy example, the parts of the text that cover the difficult example are...
Comparison of LAN Segmentation Using Bridges Switches and Routers
The CCNA exam tests your ability to compare networks that use bridges, switches, and routers to separate LAN segments. The basic workings of a bridge and a switch have already been covered in this chapter. To compare these three options, first routing logic is covered. Afterward, comparisons will be made among the three options. Routing is covered more fully in other chapters. For comparison, a router separates two segments in Figure 4-14. The client initiates the same example flow that was...
Answers to the Chapter 6 Do I Know This Already Quiz
1 What do TCP, UDP, IP, and ICMP stand for Which protocol is considered to be Layer 3-equivalent when comparing TCP IP to the OSI protocols Transmission Control Protocol, User Datagram Protocol, Internet Protocol, and Internet Control Message Protocol. Both TCP and UDP are Layer 4 protocols. ICMP is considered a Layer 3 protocol because it is used for control and management of IP. IP is the core part of the network layer (Layer 3) of TCP IP. 2 Describe how to view the IP ARP cache in a Cisco...
Destination Unreachable ICMP Message
The ICMP unreachable message is sent when a message cannot be delivered completely to the application at the destination host. However, packet delivery could fail for many reasons, so there are five separate unreachable functions (codes) using this single ICMP unreachable message. All five code types pertain directly to some IP, TCP, or UDP feature and are better described by using Figure 6-19 as an example network. Assume that Fred is trying to connect to the web server, called Web. (Web uses...
Upgrading Cisco IOS Software and the Cisco IOS Software Boot Process
50 List the commands to load Cisco IOS Software from Flash memory, a TFTP server, or ROM. 51 Prepare to back up, upgrade, and load a backup Cisco IOS Software image. Engineers need to know how to upgrade the IOS to move to a later release. Typically, a router has one IOS image in Flash memory, and that is the IOS that is used. (The term IOS image simply refers to a file containing the IOS.) The upgrade process might include steps such as copying a newer IOS image into Flash memory, configuring...
Four Steps to Answering IP Addressing Questions
You must master IP addressing and subnetting to succeed as a network engineer. To pass the CCNA exam, you must at least be able to answer a few questions about subnetting. For most networking jobs, the ability to think about IP addresses and quickly decipher the structure and meaning of the address is a prerequisite for the job. The exam will test your abilities with questions that go something like this Given a network number and a mask, how many subnets are there, and how many hosts are there...
