Cisco Exam #640-801: CCNA (MeasureUp, set 1)
Test your basic networking knowledge for Cisco's entry-level certification exam with these 15 questions and answers.
courtesy of MeasureUp
Question:
1. Which of the following is true regarding passwords on a Cisco router?
a. All passwords are encrypted.
b. A password is not active until the login command is issued for the associated line.
c. The console, auxiliary, and Telnet passwords cannot be the same.
d. Only one password can be set for all Telnet sessions.
2. A prompt such as "Router >" indicates you are in what mode?
a. Privileged mode
b. User mode
c. Setup mode
d. Configuration mode
3. When in enhanced editing mode, you can move to the beginning of a command line by pressing which of the following key sequences?
a. Ctrl-A
b. Ctrl-E
c. Esc-B
d. Esc-F
e. Ctrl-B
f. Ctrl-F
4. Where is the active configuration file of the router stored?
a. In NVRAM
b. In RAM
c. In ROM
d. In Flash memory
e. On a TFTP server
5. Which commands will display the IP addresses of all interfaces on a Cisco router? (Choose all that apply.)
a. show ip route
b. show ip address
c. show ip interface
d. show interfaces
e. display ip addresses
6. Which command would supply information about BECN and FECN?
a. show frame-relay int
b. show frame-relay map
c. show frame-relay pvc
d. show int
e. show frame-relay lmi
7. Which one of the following protocols describes the process of a TCP/IP host learning a remote host's MAC address?
a. ARP
b. SLARP
c. RARP
d. IARP
8. What is meant when the Destination Service Access Point (DSAP) is set to AA?
a. All stations with AA contained in their MAC addresses would receive this frame.
b. All stations would receive this frame because it acts like a broadcast.
c. The encapsulated protocol contained in the frame must be IP.
d. A SNAP header follows the 802.2 header.
e. The SNAP "length" field is set to 1494.
9. Which statement most correctly describes what happens on an IP over Ethernet network when one host sends data to another host?
a. Actual communications is between IP addresses.
b. Actual communications is from IP address on the sender to MAC address on the receiver.
c. Actual communications is between physical addresses.
d. Actual communications is from MAC address on the sender to IP address on the receiver.
e. On an Ethernet network, all communication is via either broadcasts or multicasts.
10. Which protocols are link-state routing protocols? (Choose all that apply.)
a. IP
b. OSPF
c. RIP
d. IPX
e. IGRP
f. Integrated IS-IS
11. Which of the following is NOT a function of the Transport Layer?
a. Provides the ability to send unacknowledged packets.
b. Can issue a "not ready" indicator.
c. Provides a non-connection oriented service.
d. Segments can be placed back into their correct sequence at the destination.
e. Provides routing services.
12. Which of the following would most likely use the protocol TCP? (Choose three.)
a. DNS
b. FTP
c. TFTP
d. Telnet
e. SNMP
f. SMTP
13. What protocol would be needed to send a host unreachable message to a source host?
a. ARP
b. FTP
c. ICMP
d. RARP
e. SNMP
14. How can split horizon best be described?
a. It is a Cisco proprietary feature of switches, which prevents a bridge from sending frames to a network segment that does not contain the destination host.
b. It is a calculation in a router that limits the maximum size of a packet that a particular interface can route.
c. It is a feature of a router that helps prevent routing loops by preventing routing updates from including information about routes to remote networks that were learned through the interface the update is being sent from.
d. It is a feature of routers to help reduce the convergence time.
15. What is the maximum number of subnets that can be assigned to network 172.16.0.0 if you use a subnet mask of 255.255.240.0?
a. 14
b. It is an invalid subnet mask for the network given.
c. 16
d. 32
e. 30
1. B is true. A password is not active until the login command is issued for the associated line. The enable password, used to enter privileged mode, is not encrypted. The enable secret password is encrypted. The console, auxiliary, and Telnet passwords are all set separately. You can enter any password for any of the lines. All configured vtys typically have the same password, but it is not required. If you want, you can set a different password on each vty line.
2. B is correct. There are three major command prompts that you should be able to recognize. They are:
- "router>" This prompt indicates you are in user mode, sometimes called user exec mode. This mode has very limited capabilities other than being able to issue the "enable" command, which takes you the next level known as privileged exec mode.
- "router#" This prompt indicates you are in privileged exec mode, sometimes called enable mode or privileged mode. It is a powerful command-line context because it can get you into global configuration mode. The most powerful commands for troubleshooting in privileged mode are the "show" commands. Issue the "config t" command to enter global configuration mode.
- "router(config)#" This prompt indicates you are in configuration mode or sometimes called global configuration mode because changes made to the configuration files in this mode affect the entire router, not just a specific interface on the router.
Setup mode, sometimes called Initial Configuration mode is not characterized by a unique command prompt. It is used typically when the router first boots and no configuration files are saved in non-volatile random access memory (NVRAM). You can start the "setup mode" by typing "setup" in privileged mode.
3. A is correct. The Cisco IOS offers several key sequences called hot keys that are designed to allow you to move around the command line more quickly if you need to edit a command string. These hot keys can come in handy if you Telnet into the router with an old Telnet program.
Some older terminal programs do not supply the proper keystrokes needed for command-line editing. The hot keys built into the IOS will overcome this limitation.
The key sequences are defined as follows:
- Ctrl-A - moves cursor to the beginning of the line.
- Esc-B - moves the cursor back one word in the current command.
- Ctrl-B - moves the cursor backward one space at a time without deleting text.
- Esc-F - moves the cursor ahead one word in the current command.
- Ctrl-E - moves the cursor to the end of the line.
- Esc-F - moves the cursor forward one word.
4. B is correct. The active configuration file is called "running-config" and is stored in RAM. Routers have the following types of memory installed:
- Random Access Memory (RAM) - volatile memory that stores running-config, routing tables and any information that is dynamic in nature.
-
Read Only Memory (ROM) - permanent memory that contains the basic instruction set that boots the router (bootstrap). The following are stored in ROM:
- rxboot, which is a limited feature IOS
- ROM Monitor (ROMMON), which is used for password recovery
- Flash Memory - non-volatile memory that can serve as a storage area for config files and the full IOS image files. Routers can run the IOS from Flash.
- NVRAM - Non-Volatile RAM is where the startup-config file is saved. This memory area has a battery backup to preserve its contents.
Routers can boot from a TFTP server, but the active configuration file is stored in the local RAM.
5. C and D are correct. Both "show ip interface" and "show interfaces" will list IP addresses with the associated interface.The command "show ip route" displays the contents of the routing table. The command "show ip address" does not exist. The command "display ip addresses" also does not exist.
6. C is correct. Backward Explicit Congestion Notification (BECN) is used in a Frame Relay network. When a Frame Relay switch recognizes congestion in the network, it sets the BECN bit in the Frame Relay packet traveling backward to the source router, instructing the router to reduce the rate at which it is sending packets. It is used to track congestion in a permanent virtual circuit (PVC).
Forward Explicit Congestion Notification (FECN) is used in a Frame Relay network. When a Frame Relay switch recognizes congestion in the network, it sets the FECN bit in the Frame Relay packet traveling forward to the destination device, indicating that congestion was detected in the path used.
Frame Relay uses permanent virtual circuits (PVC), which are permanent logical circuits that represent the paths that frames travel between end units. BECN and FECN values are shown when you enter the "show frame-relay pvc" command.
The Frame-Relay "show frame-relay" command line options are as follows:
-
Router-A# show frame-relay ?
-
ip show frame relay IP statistics
-
lapf show frame relay lapf status/statistics
-
lmi show frame relay lmi statistics
-
map Frame-Relay map table
-
pvc show frame relay pvc statistics
-
qos-autosense show frame relay qos-autosense information
-
route show frame relay route
-
svc show frame relay SVC stuff
-
traffic Frame-Relay protocol statistics
So, judging from the list above, the correct answer would be:
Router-A#show frame-relay pvc
The output from this command would be as follows:
PVC Statistics for interface Serial0/0 (Frame Relay DTE)
DLCI = 100, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0
input pkts 24 output pkts 5 in bytes 6526
out bytes 520 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 0 out bcast bytes 0
pvc create time 00:13:09, last time pvc status changed 00:08:17
Notice the BECN and FECN packet count in the above printout.
The "show frame-relay lmi" command lists Local Management Interface (LMI) statistics on an interface configured for Frame Relay encapsulation. It does not display BECN or FECN statistics.
The "show frame-relay map" command lists the interface, IP address, and Data Link Connection Identifier (DLCI) information but does not display BECN or FECN statistics.
The "show int" command displays up-down status on all interfaces but not the BECN or FECN statistics.
The "show frame-relay int" command uses the wrong syntax as indicated in the "show frame-relay ?" display shown above.
7. A is correct. Address Resolution Protocol (ARP) maps a known Logical Address (IP Address) to a Physical Address (MAC Address).
When a host wants to send traffic to a host that isn't on the local segment, the first thing it does is ARP for its default gateway. It sends out a message that says something like: "I know my gateway is 192.168.1.1, but I don't know the MAC address. I checked my ARP cache and didn't see an entry that mapped 192.168.1.1 to a MAC address...can someone tell me who this is?"
IARP (Inverse Address Resolution Protocol) is what Frame Relay uses to map a data link connection identifier (DLCI) to an IP address.
SLARP (Serial Line Address Resolution Protocol) is used when a router attempts to request an IP address for a serial interface.
RARP (Reverse Address Resolution Protocol) is the exact opposite of ARP (mapping a known MAC address to an unknown IP address). This was used by "diskless" workstations to get an IP address. It is somewhat similar to DHCP.
8. D is correct. Each Data Link header has a field in its header with a code that defines the type of protocol header that follows. The IEEE called its Type field the destination service access point (DSAP). It is only one byte long, which is not big enough to number all the protocols. To accommodate more protocols, the IEEE allowed the use of an extra header, called the Subnetwork Access Protocol (SNAP) header. When the DSAP field is set to hex AA, this implies that a SNAP header follows the 802.2 header. The SNAP header includes a two-byte protocol type field so all possible protocols can be identified.
Setting both the Source Service Access Point (SSAP) and the Destination Service Access Point (DSAP) fields to "AA" indicates that SNAP is in use.
SNAP eliminates the limitations of the LLC. The SNAP header allows for a varying "type" field to allow for as many protocols as necessary. This allows LLC to identify and handle protocols that it was not originally designed to handle.
SNAP provides for backward compatibility of older protocols.
The "AA" setting does not set the protocol to IP or specify what the MAC address has to be to receive the frame.
The SNAP header contains a "type" field, not a "length" field.
9. C is correct. In a TCP/IP network, logical addressing using IP addresses is used to identify the source or host IP address and the final destination IP address. But an IP packet may (and most likely will) traverse the internetwork by passing through many different Data Link technologies. The IP packet may originate on an Ethernet segment, pass through a Frame Relay, ATM, HDLC, and PPP segment on the way to the destination. Each Data Link protocol will use the MAC address of the next hop router to build the destination MAC address in the associated header. This is the process of routing.
One of the sub-components of the Data-Link Layer (Layer 2) is the MAC sublayer. The MAC sublayer protocols deal with the Media Access Control (MAC) address of the sending and receiving network nodes.
Take a look at the components of a 802.3 Frame below:
| Preamble | DA | SA | Length | Data | FCS |
If you looked at the data in both the Destination Address (DA) and the Source Address (SA) fields, you would see MAC Addresses of the nodes involved in the data transmission.
10. B and F are correct. Link-state routing protocols have the following characteristics:
1) They build and maintain a database of the network topology.
2) The database is built from the information learned via Link-State Packets (LSPs).
3) They only send incremental topology updates.
4) They rely on the Shortest Path First (SPF) algorithm to analyze routing updates.
5) They allow the creation of larger hierarchical network topologies.
6) They support classless addressing.
7) They allow route summarization.
Of the choices given, only OSPF and Integrated IS-IS are link-state routing protocols.
-
OSPF - uses route "cost" as a metric (not hop count), maintains a network topology database, runs the SPF algorithm, and sends incremental updates.
-
Integrated IS-IS (Intermediate System-to-Intermediate System) is also a link-state protocol. It supports VLSM, converges quickly, and updates incrementally every 15 minutes.
-
RIP - relies on hop count, sends entire routing table at each update interval. It is a Distance vector protocol.
-
IGRP - uses a composite metric (not hop count), sends routing table to neighbors at 90 second intervals. It is a Distance vector protocol.
-
IP - Layer 3 protocol, provides connection-less transmission of data. It is a routed protocol, not a routing protocol.
-
IPX - uses "ticks" or "hops" as a metric, broadcasts entire routing table. It is a routed protocol, not a routing protocol.
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11. E is correct. The Transport Layer is responsible for setting up and defining how two nodes will communicate. Since the Transport Layer resides above the Network Layer, it is tasked with assembling and disassembling segments and preparing them for dissemination over the network infrastructure. It is at the Transport Layer that most of the network error detection and error correction takes place.
In addition, the Transport Layer can "speak" both reliably (TCP - a connection-oriented protocol) and unreliably (UDP - a connectionless protocol).
The Transport Layer ...
-
... can issue a "not ready" indicator (TCP).
-
... arranges segments back into their proper order at the destination.
-
... can provide the ability to send unacknowledged packets.
-
... can provide a non-connection oriented service (UDP).
Routing services are provided by routers, which operate at the Network Layer, not the Transport Layer.
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12. B, D and F are correct. To answer this question, you need to look at each protocol and determine whether it requires a connection-oriented (reliable) session (TCP) or a connectionless session (UDP). A connection-oriented session supports error detection and correction. If packets are lost during transfer, the lost packets will be identified and retransmitted. A connectionless session is not concerned about losing packets, and no error correction is attempted. If data transfer fails, the originating host simply requests the data again.
File Transfer Protocol (FTP) transfers files between two nodes, so it is very important that the communication pipeline is monitored and is considered reliable. FTP requires a TCP session.
Telnet most certainly requires a connection oriented (reliable) communications session to function. Telnet is a remote control between two stations.
Simple Mail Transport Protocol (SMTP) should not to be confused with SNMP. It is the protocol responsible for delivery of mail throughout the internetwork. Receipt of e-mail is important and requires a reliable delivery pipeline such as TCP.
Domain Name System (DNS) can use either TCP or UDP ports. A DNS request generally uses UDP since it is a request for an IP address for a fully qualified domain name. It would not require a reliable two-way communication pipe. Since the question specifies "what would be the most likely", UDP would be the most correct answer.
Trivial File Transfer Protocol (TFTP) provides only the most basic of file transfer capabilities. It does not require you to log in. It just sits there and waits for files to come in. TFTP uses IP for addressing and UDP at layer 4.
Simple Network Management Protocol (SNMP) is a passive protocol that handles MIB queries by sending out UDP responses. The requester interrogates the SNMP capable Router (a string called an OID) and the router responds with the information requested. It sounds connection oriented, but it's actually a series of UDP conversations.
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13. C is correct. The Internet Control Message Protocol (ICMP) is a helper protocol for IP to deliver messages. Some ICMP messages are Destination Unreachable, Source Quench, Echo, and Address Request. Each of these ICMP messages is carried in IP datagrams.
Address Resolution Protocol (ARP) is used by TCP/IP to find the MAC address of a node whose IP address you already know. The ARP request is broadcast (as an all station announcement) to all the nodes on the segment. Only the host with the matching IP address responds with its MAC address.
File Transfer Protocol (FTP) is an Application layer protocol that is used to transfer files back and forth between hosts.
Reverse Address Resolution Protocol (RARP) is used by TCP/IP to find the IP address of a node whose MAC address you already know.
Simple Network Management Protocol (SNMP) is an Application layer protocol that is used to interrogate devices and return system performance metrics.
14. C is correct. The split horizon rule says, "Never announce a routing update back to the router that originally told you about it."
This technique attempts to prevent routing loops from occurring by eliminating the source of an update from the list of routers that will receive the update. Split horizon is designed to fix the "counting to infinity" problem. This is best described by an example:
Router-A tells Router-B that its route to network 1 has failed at about the same time that Router-B advertises a valid path to network 1. If routing update information crosses paths, a never-ending cycle of updates begins with one router saying the link is up and the next router says it's down. Then, both routers accept the update from each other and announce the opposite information back to each other. This would go back and forth for an infinity of cycles if not managed. Split horizon provides the procedure to prevent this problem.
Split horizon is a feature of routers, not bridges or switches. Preventing a bridge from sending frames to a network segment that does not contain the destination host is exactly what switches are supposed to do. A bridge looks up the destination address in its bridge table and forwards it to the proper segment. This is standard bridge/switch operation and has nothing to do with Split horizon.
Split horizon is not a calculation in a router that limits the maximum size of a packet that a particular interface can route. The maximum packet size that a router interface can route is called the maximum transmission unit (MTU).
Split horizon is not designed to help reduce convergence time. Convergence time is a general term that describes the length of time it takes for routers to completely update routing tables.
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15. A is correct. The IP address given, 172.16.0.0, 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 there are 20 network bits (/20) total and 12 host bits. Therefore, 4 bits in the third octet are used for subnetting.
If you converted this subnet mask to binary, you would have the pattern:
11111111.11111111.11110000.00000000
To determine the number of subnets, you use the 2^N-2 formula on the number of subnet bits (4). This yields:
16 - 2 = 14 networks (subnets)
To calculate the range of host addresses per network, use the 2^N-2 formula on the number of host bits (12). This yields:
4096- 2 = 4094 (hosts per subnet)
An easy way to determine what IP addresses are available is to use the following table:
128 064 032 016 008 004 002 001
128 192 224 240 248 252 254 255
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 left like this, 1, 2, 4, 8, 16, 32, 64, 128. Next, starting from the left, add the number in the top row to the previous number in the bottom row like this: 128, 128 + 64 = 192, 192 + 32 = 224, 224 + 16 = 240, 240 + 8 = 248, 248 + 4 = 252, 252 + 2 = 254, 254 + 1 = 255.
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 172.16.0.0 and increments by 16 in the third octet for a total of 14 subnets. The resulting subnets are:
172.16.0.0
172.16.16.0
172.16.32.0
172.16.48.0
Repeating this pattern all the way to the last subnet 172.16.240.0
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 16 subnets, but the formula says to delete two of them, the first, and the last.
So, the maximum number of subnets that can be assigned to network 172.16.0.0 if you use a subnet mask of 255.255.240.0 is 14.
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