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PopQuiz Cisco Exam #640-801: CCNA (MeasureUp, set 3) Test your basic networking knowledge for Cisco's entry-level certification exam with these 10 questions and answers. courtesy of MeasureUp 1. Answer D is correct. The address is illegal because it has a value of zero (0) in the first octet. The class of an IP address is determined by the value of the first octet. First Octet Rules:
The above rules provide the following ranges:
Refer to the following attempt to assign the above illegal address:
Enter configuration commands, one per line:
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2. Answers A and B are correct. Local Management Interface (LMI) is the protocol used between Frame Relay Data Terminal Equipment (DTE) and Data Communications Equipment (DCE) to manage a connection. The LMI type is only locally significant. LMI is communication between the local router and the local frame relay switch. The remote router and the remote frame relay switch can use different LMI types. Three LMI protocol types are available in Cisco IOS software: Cisco, International Telecommunications Union (ITU) (q933a), and American National Standards Institute (ANSI). Each LMI option is slightly different and therefore is incompatible with the other two. As long as both the DTE and DCE on each end of an access link use the same LMI standard, LMI works fine. This line is unnecessary since the LMI type cisco is the default and sets the LMI type to autosensed. If the LMI is autosensed, either "cisco", "ansi", or "q933a" can be used on the other end of the link. This command is not incomplete and the Data Link Connection Identifier (DLCI) for the interface must still be configured. The following configuration shows a switch between a network using two different LMI types:
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3. Answers A and B are correct. When you boot the router, the startup-configuration file, which is stored in non-volatile random access memory (NVRAM), is moved to random access memory (RAM). Of course, you could manually move it to RAM using the "copy start run" command. The "copy run start" command will take the currently running-config and write it to the startup-config file. This is normally done after configuring the router with the desired settings. To save the settings, copy the contents of running-config to startup-config before shutting down the router or the settings will be lost. Any command that has "show" in its command is a passive command that will only allow you to list or view information. "Show startup-config" displays the content of the startup-configuration used during bootup. "Show running-config" displays the settings presently being used by the router.
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4. Answer E is correct. The configuration example above is correct for setting a password to the console port. Cisco switches use an Internetwork Operating System (IOS) for configuration very similar to the one that is used on routers. The only differences are in the choices for each command. There are several ways to control access to a Cisco switch. You can password protect access via the console and via a Telnet session. After passing these login passwords, you will be in User mode with very limited access to the switch configuration. Two password options can be used to access Privileged mode, where more powerful commands can be entered. The "enable password" command will establish the password needed to enter privileged EXEC mode. It is a clear text password and is not considered very secure. The "enable secret" command can be used to create an encrypted password. Both control access to privileged mode. There are no login names used in the Cisco IOS. The command "login" tells the router to display a login prompt when attempting to login. The command "password cisco" sets the console login password to "cisco". You would configure the login for Telnet sessions by first entering "vty 0 15". You cannot Telnet to the console port. It requires a direct connection using terminal emulation software such as Windows HyperTerminal.
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5. Answer C is correct. The IP address given, 165.20.90.90/20, is a Class B network which has a default subnet mask of 255.255.0.0. The subnet mask used in this problem is 255.255.240.0, which means that you have 20 network bits (/20) total and 12 host bits. Therefore, four bits in the third octet are used for subnetting. If you converted this subnet mask to binary, you would have the following pattern:
To determine the number of subnets, use the 2^N-2 formula on the number of subnet bits (4). This yields:
To calculate the range of host addresses per network, use the 2^N-2 formula on the number of host bits (12). This yields:
Use the following table to determine what the available IP addresses are:
Notice that this table is built by first writing the number one (001) starting at the right margin, then doubling it successively from right to Using this table, find the subnet mask number you are working with in the lower row. In this case you are using the 240 from the third octet. Take the number directly above the 240, which is 16, and this is the incremental value of the subnet numbers in the associated octet (the third octet in this case).This means that the subnet numbers begin with 165.20.0.0 and increment by 16 in the third octet for a total of 6 subnets. The resulting subnets are:
Repeating this pattern all the way to the last subnet:
Notice that you begin with the zero subnet and carry it through to the subnet with the same number as the subnet mask. This yields 14 subnets, but the formula says to delete two of them: the first and the last. The IP address in the question, 165.20.90.90, would therefore fall in the range between 165.20.80.0 and 165.20.96.0. There are 4094 usable IP addresses in this range. You cannot use the first, 165.20.80.0, because this is the subnet number itself. This number cannot be assigned to a host. The last number in this subnet is 165.20.95.255, but this cannot be assigned to a host because this is the broadcast address for the subnet. That leaves you with the first usable IP address of 165.20.80.1, and all addresses between it and the broadcast address are valid. Therefore, the host with IP address 165.20.90.90/20 is in subnet 165.20.80.0.
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6. Answer D is correct. If you forget how a command is spelled, or what the exact command is, you can use the "?" to help you complete the command. This is known as "context sensitive" help. To see a list of the options available for a command, type the command, followed by a space and a question mark, and you will receive a list of available options for the command you typed. If you do not even know what commands are available, simply type the ? and a list of available commands is displayed. If you have forgotten how to spell a certain command, but remember it begins with the letters "cl", type "cl?" (notice no space between the l and the ?) and the context sensitive help mode of the command line interface will list all commands available that begin with "cl". In this case, the user has either mis-keyed a character or is not sure what the command should be. Since the error occurred at the "t" in "art", you can substitute a question mark for the "t" to find valid commands beginning with "ar". Refer to the following:
The following is an example of the context sensitive help mode, available in all Cisco routers and switches, showing the options available for a particular command:
The router context sensitive help displays command line options that are available for this major command. If you use "show ar ?", it would be ambiguous, as shown below:
If you simply typed "?", you would get a list of all commands available in privileged mode, and it would not help to determine the correct spelling of the subcommand under "show". If you typed "show arp", the command would display the contents of the arp cache. It would not be the most likely command to enter because the user would have entered it in the first place if he knew it.
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7. Answers B and C are correct. The "show run" command is the short form for "show running-config". It is one of the most useful commands used to see the current, active configuration of a router. This command displays the details of all interfaces, whether they are completely configured or not, including both IP and IPX. The "show protocol" command also lists details for all protocols configured on a router. An example of the output of the "show protocol" command is shown below:
The "show ip protocol" command will show just the ip routing protocols that are currently configured, not IPX, Appletalk, or any others. The following is an example output of the "show ip protocol" command:
Show start will display the contents of the startup-config file, which may or may not show all the currently routed protocols.
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8. Answer C is correct. The router is very similar to a PC and will store its power-on diagnostics in read only memory (ROM). You can enter the router's diagnostic mode by modifying the configuration register and changing the configuration register bit number 15 (hex # 0x8000) to 1. This will ignore the non-volatile random access memory (NVRAM) startup-configuration file and put the router in diagnostic mode. The configuration register is a 16-bit register in the router, which is used to set the startup process for the router. The important bits of the configuration register are:
The startup-configuration file is stored in NVRAM. The full-featured Internetwork Operating System (IOS) is stored in Flash. The running-configuration file is stored in random access memory (RAM).
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9. Answer A is correct. From one perspective, switches are bridges with lots of ports and faster internal processing. A switch is very similar to a bridge in that they both deal exclusively with Layer 2 addresses. A switch learns the location of devices based on the interface to which they are connected. They both rely on the spanning tree algorithm to provide loop-free paths to a destination. Switches form a separate collision domain for each port. All ports on bridges and switches are in the same broadcast domain. Routers separate LAN segments into multiple broadcast domains. A router makes forwarding decisions based on IP addresses. A bridge or switch increases available bandwidth because it creates separate collision domains for each port. A router creates separate broadcast domains for each interface. An active hub is a powered hub that acts like a multiport repeater. A concentrator is another name for an active hub. Neither breaks up a LAN segment into multiple collision domains. A passive hub forms a single collision domain but does not act like a repeater like an active hub does.
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10. Answer B is correct. "Handshaking" is the process of initiating, acknowledging, and confirming a TCP connection. It is a three step process as outlined below: Step One: Host A --(Seq 100) SYN --> Host B Host A wants to initiate a connection with Host B. It sends out a SYN (Synchronize) segment saying something like:
Host A also sends this sequence number so that Host B will know what number to expect in the next transmission. Step Two: Host A <-- SYN/ACK (Seq 300) -- Host B Host B sends back a SYN/ACK (Acknowledge) segment saying something like:
Host B also sends a sequence number, so Host A will know what number to Step Three: Host A -- ACK (Seq 101) --> Host B Host A sends back an ACK (Acknowledge) segment saying something like:
To start a TCP connection, TCP uses the three-way connection-establishment sequence as described above. To terminate a connection, a four-way termination sequence is used, adding a FIN bit to the sequence. The termination sequence is described as ACK, FIN; ACK; ACK, FIN; ACK.
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