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CCNA WAN Questions

Here you will find answers to WAN Questions

Question 1

Users have been complaining that their Frame Relay connection to the corporate site is very slow. The network administrator suspects that the link is overloaded. Based on the partial output of the Router#show frame relay pvc command shown in the graphic, which output value indicates to the local router that traffic sent to the corporate site is experiencing congestion?

A. DLCI=100
B. last time PVC status changed 00:25:40
C. in BECN packets 192
D. in FECN packets 147
E. in DF packets 0

Answer: C

Question :2

When troubleshooting a Frame Relay connection, what is the first step when performing a loopback test?

A. Set the encapsulation of the interface to HDLC.
B. Place the CSU/DSU in local-loop mode.
C. Enable local-loop mode on the DCE Frame Relay router.
D. Verify that the encapsulation is set to Frame Relay.

Answer: A

Explanation

The first thing when performing a loopback test on a Frame Relay connection is to reconfigure the encapsulation of the interface to HDLC protocol instead of Frame Relay protocol. The main reason is Frame Relay requires a pair of DCE/DTE which cannot be used in a loopback test.

For more information about steps of trouble shooting Frame Relay, please read: http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml#topic20

For your information, below is a paragraph quoted from the above link:

“Serial0 is down, line protocol is down”

This output means you have a problem with the cable, channel service unit/data service unit (CSU/DSU), or the serial line. You need to troubleshoot the problem with a loopback test. To do a loopback test, follow the steps below:

1. Set the serial line encapsulation to HDLC and keepalive to 10 seconds. To do so, issue the commands encapsulation hdlc and keepalive 10 under the serial interface.
2. Place the CSU/DSU or modem in local loop mode. If the line protocol comes up when the CSU, DSU or modem is in local loopback mode (indicated by a “line protocol is up (looped)” message), it suggests that the problem is occurring beyond the local CSU/DSU. If the status line does not change states, there is possibly a problem in the router, connecting cable, CSU/DSU or modem. In most cases, the problem is with the CSU/DSU or modem.
3. Ping your own IP address with the CSU/DSU or modem looped. There should not be any misses. An extended ping of 0×0000 is helpful in resolving line problems since a T1 or E1 derives clock from data and requires a transition every 8 bits. B8ZS ensures that. A heavy zero data pattern helps to determine if the transitions are appropriately forced on the trunk. A heavy ones pattern is used to appropriately simulate a high zero load in case there is a pair of data inverters in the path. The alternating pattern (0×5555) represents a “typical” data pattern. If your pings fail or if you get cyclic redundancy check (CRC) errors, a bit error rate tester (BERT) with an appropriate analyzer from the telco is needed.
4. When you are finished testing, make sure you return the encapsulation to Frame Relay.

Question 3

What occurs on a Frame Relay network when the CIR is exceeded?

A. All TCP traffic is marked discard eligible.
B. All UDP traffic is marked discard eligible and a BECN is sent.
C. All TCP traffic is marked discard eligible and a BECN is sent.
D. All traffic exceeding the CIR is marked discard eligible.

Answer: D

Explanation

Committed information rate (CIR): The minimum guaranteed data transfer rate agreed to by the Frame Relay switch. Frames that are sent in excess of the CIR are marked as discard eligible (DE) which means they can be dropped if the congestion occurs within the Frame Relay network.

Note: In the Frame Relay frame format, there is a bit called Discard eligible (DE) bit that is used to identify frames that are first to be dropped when the CIR is exceeded.

Question 4

What are two characteristics of Frame Relay point-to-point subinterfaces? (Choose two)

A. They create split-horizon issues.
B. They require a unique subnet within a routing domain.
C. They emulate leased lines.
D. They are ideal for full-mesh topologies.
E. They require the use of NBMA options when using OSPF.

Answer: B C

Question 5

The output of the show frame-relay pvc command shows ”PVC STATUS=INACTIVE”. What does this mean?

A. The PVC is configured correctly and is operating normally,but no data packets have been detected for more than five minutes.
B. The PVC is configured correctly, is operating normally and is no longer actively seeking the address the remote route,
C. The PVC is configured correctly, is operating normally and is waiting for interesting to trigger a call to the remote router.
D. The PVC is configured correctly on the local switch, but there is a problem on the remote end of the PVC.
E. The PVC is not configured on the switch.

Answer: D

Explanation

The PVC STATUS displays the status of the PVC. The DCE device creates and sends the report to the DTE devices. There are 4 statuses:

+ ACTIVE: the PVC is operational and can transmit data
+ INACTIVE: the connection from the local router to the switch is working, but the connection to the remote router is not available
+ DELETED: the PVC is not present and no LMI information is being received from the Frame Relay switch
+ STATIC: the Local Management Interface (LMI) mechanism on the interface is disabled (by using the “no keepalive” command). This status is rarely seen so it is ignored in some books.

Question 6

Which encapsulation type is a Frame Relay encapsulation type that is supported by Cisco routers?

A. Q933-A Annex A
B. IETF
C. ANSI Annex D
D. HDLC

Answer: B

Explanation

Cisco supports two Frame Relay encapsulation types: the Cisco encapsulation and the IETF Frame Relay encapsulation, which is in conformance with RFC 1490 and RFC 2427. The former is often used to connect two Cisco routers while the latter is used to connect a Cisco router to a non-Cisco router. You can test with your Cisco router when typing the command Router(config-if)#encapsulation frame-relay ? on a WAN link. Below is the output of this command (notice Cisco is the default encapsulation so it is not listed here, just press Enter to use it).

Note: Three LMI options are supported by Cisco routers are ansi, Cisco, and Q933a. They represent the ANSI Annex D, Cisco, and ITU Q933-A (Annex A) LMI types, respectively.

HDLC is a WAN protocol same as Frame-Relay and PPP so it is not a Frame Relay encapsulation type.

Wan Technologies

Question 1

The command frame-relay map ip 10.121.16.8 102 broadcast was entered on the router. Which of the following statements is true concerning thiscommand?

A: This command should be executed from the global configuration mode.

B: The IP address 10.121.16.8 is the local router port used to forward data.

C: 102 is the remote DLCI that will receive the information.

D: This command is required for all Frame Relay configurations.

E: The broadcast option allows packets, such as RIP updates, to be forwarded across the PVC.

Correct Answers: E

Explanation:

The command frame-relay map ip 10.121.16.8 102 broadcast means to mapping the distal IP 10.121.16.8 102 to the local DLCI 102. When the “broadcast” keyword is included, it turns Frame Relay network as a broadcast network, which can forward broadcasts

Question 2

Refer to the exhibit. Which statement describes DLCI 17?

A: DLCI 17 describes the ISDN circuit between R2 and R3.

B: DLCI 17 describes a PVC on R2. It cannot be used on R3 or R1.

C: DLCI 17 is the Layer 2 address used by R2 to describe a PVC to R3.

D: DLCI 17 describes the dial-up circuit from R2 and R3 to the service provider.

Correct Answers: C

Explanation:

DLCI stands for Data Link Connection Identifier. DLCI values are used on Frame Relay interfaces to distinguish between different virtual circuits. DLCIs have local significance because the identifier references the point between the local router and the local Frame Relay switch to which the DLCI is connected.

Question 3

A default Frame Relay WAN is classified as what type of physical network?

A: point-to-point

B: broadcast multi-access

C: nonbroadcast multi-access

D: nonbroadcast multipoint

E: broadcast point-to-multipoint

Correct Answer: C

Explanation:

Non-Broadcast Multi-Access (NBMA) networks are types such as Frame Relay, X.25, and Asynchronous Transfer Mode (ATM). These networks allow for multi-access, but have no broadcast ability like Ethernet

Question 4

Which of the following are key characteristics of PPP? (Choose three.)

A: can be used over analog circuits

B: maps Layer 2 to Layer 3 address

C: encapsulates several routed protocols

D: supports IP only

E: provides error correction

Correct Answers: A C E

Explanation

Below is some more information about PPP:

PPP (Point-to-Point Protocol) allows authentication such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP) and multilink connections (allow several separate physical paths to appear to be one logical path at layer 3) and can be run over asynchronous and synchronous links.

PPP can work with numerous network layer protocols, including Internet Protocol (IP), Novell’s Internetwork Packet Exchange (IPX), NBF and AppleTalk.

PPP only supports error detection, not error correction so answer E should be understood as “provides error detection”. It is a mistake of this question.

Question 5

Which three Layer 2 encapsulation types would be used on a WAN rather than a LAN? (Choose three)

A: HDLC

B: Ethernet

C: Token Ring

D: PPP

E: FDDI

F: Frame Relay

Correct Answer: A D F

Question 6

Refer to the exhibit. What is the meaning of the term dynamic as displayed in the output of the show frame-relay map command shown?

A: The Serial0/0 interface is passing traffic.

B: The DLCI 100 was dynamically allocated by the router

C: The Serial0/0 interface acquired the IP address of 172.16.3.1 from a DHCP server

D: The DLCI 100 will be dynamically changed as required to adapt to changes in the Frame Relay cloud

E: The mapping between DLCI 100 and the end station IP address 172.16.3.1 was learned through Inverse ARP

Explanation

The term dynamic indicates that the DLCI number and the remote router IP address 172.16.3.1 are learned via the Inverse ARP process.

Inverse ARP is a technique by which dynamic mappings are constructed in a network, allowing a device such as a router to locate the logical network address and associate it with a permanent virtual circuit (PVC).

Correct Answer: E

Question 7

Which of the following describes the roles of devices in a WAN? (Choose three.)

A: A CSU/DSU terminates a digital local loop

B: A modem terminates a digital local loop

C: A CSU/DSU terminates an analog local loop

D: A modem terminates an analog local loop

E: A router is commonly considered a DTE device

F: A router is commonly considered a DCE device

Correct Answers: A D E

Question 8

How should a router that is being used in a Frame Relay network be configured to avoid split horizon issues from preventing routing updates?

A: Configure a separate sub-interface for each PVC with a unique DLCI and subnet assigned to the sub-interface

B: Configure each Frame Relay circuit as a point-to-point line to support multicast and broadcast traffic

C: Configure many sub-interfaces on the same subnet

D: Configure a single sub-interface to establish multiple PVC connections to multiple remote router interfaces

Correct Answer: A

Question 9

What can a network administrator utilize by using PPP Layer 2 encapsulation? (Choose three.)

A: VLAN support

B: compression

C: authentication

D: sliding windows

E: multilink support

F: quality of service

Correct Answers: B C E

Question 10

The Frame Relay network in the diagram is not functioning properly. What is the cause of the problem?

A: The Gallant router has the wrong LMI type configured

B: Inverse ARP is providing the wrong PVC information to the Gallant router

C: The S3 interface of the Steele router has been configured with the frame-relay encapsulation ietf command

D: The frame-relay map statement in the Attalla router for the PVC to Steele is not correct

E: The IP address on the serial interface of the Attalla router is configured incorrectly

Correct Answer: D

Explanation

At Attalla router, we find a deleted status but the next map statement indicates an active status, which if for Gallant. Therefore we can deduce the map statement for the PVC from Attalla to Steele is incorrect. Incorrect DLCI assignments that are configured normally shown up as “deleted” in the frame relay maps.

What is the difference between OSPF and RIP?

RIP and OSPF are both routing protocols likely you have used without even knowing it. A routing protocol describes the way your data (or signals) get from your PC on a network to another PC or device on the network.

RIP = Hop count Algorithm

The only metric used to calculate the cost of a path (path is from point A to destination B) is the hop count from router A to router B, even if you have a path with more hops and more bandwidth available.

OSPF = Link State Algorithm

This is a more intelligent algorithm, tha build a topology of network and build the cost regarding some characteristics of path like bandwidth, load, reliability, etc.A real life example would be like when work is done and its time to drive home. You have multiple routes usually to choose from to get home. The shortest way home would obviously be a straight line from work to home. Unfortunately no magic road exists from where ever you are directly to where ever you need to go. So if you were using RIP to get home you would drive in a straight line (or take the roads that would more or less offer you a straight route home). Thing is, these roads may be BUSY, very busy in fact, you can sit in traffic for a half hour moving less than 1km sometimes. So technically the shortest way (straight line) may not be the most efficient way. Now if you were using OSPF, you would take into account traffic and other variables to decide how to get home. The quickest route home may not be the direct path, it may be a back road that has less traffic on it, through a sub division, and then to your house. However because you were using OSPF you got home quicker than if you were to use RIP as RIP didn’t really look at what the traffic was like. Now in the above paragraph turn the word “work” into “client” and the word “home” into “server” and replace the word “you” with “the packet” – magically we turn the above paragraph into tecnobabble

Back

what is Connection oriented and Connectionless

Difference Between Connection oriented vs Connection less

Connection-oriented means that a connection (a virtual link) must be established before data can be exchanged. This can guarantee that data will arrive, and in the same order it was sent. It guarantees delivery by sending acknowledgements back to the source when messages are received.

Example

TCP is an example of an connection-oriented transport protocol.

A common example of connection-oriented communication is a telephone call: you call, the ‘destination’ picks up the phone and acknowledges and you start talking (sending data). When a message or a piece of it doesn’t arrive, you say: “What!?” and the sender will retransmit the data.

Connectionless is the opposite of connection-oriented; the sender does not establish a connection before it sends data, it just sends without guaranteeing delivery.

Example

UDP is an example of an connectionless transport protocol.

Application Layers

Host A————————————Host B

Application layer——-data————Application layer

Presentation layer—–data————Presentation layer

Session layer———–data————Session layer

Transport layer—–segments——–Transport layer

Network layer ——packets———-Network layer

Data-link layer——-frames———–Data-link layer

Physical layer———–bits————-Physical layer

Back

CCNA – EIGRP Questions

Here you will find answers to EIGRP Questions

Question 2:

As a Cisco technician, you need to know EIGRP protocol very well. Which of the following is true about EIGRP successor routes? (Choose two)

A – A successor route is used by EIGRP to forward traffic to a destination
B – Successor routes are stored in the neighbor table following the discovery process
C – Successor routes are flagged as “active” in the routing table
D – A successor route may be backed up by a feasible successor route

Answer: A D

Explanation:

B is not correct because neighbor table only contains a list of directly connected EIGRP routers that have an adjacency with this router, it doesn’t contain successor routes.

C is not correct because successor routes are not flagged as “active”, they are always the best route to reach remote networks and are always used to send packets.

A and D are correct because successor route is the best and primary route to a remote network. It is stored in the routing table and topology table. If this route fails, a backup route (called feasible successor route) in the topology table will be used to route traffic to a destination.

Question 3:

Which two statements are true regarding EIGRP? (Choose two)

A – Passive routes are in the process of being calculated by DUAL
B – EIGRP supports VLSM, route summarization, and routing update authentication
C – EIGRP exchanges full routing table information with neighboring routers with every update
D – If the feasible successor has a higher advertised distance than the successor route, it becomes the primary route
E – A query process is used to discover a replacement for a failed route if a feasible successor is not identified from the current routing information

Answer: B E

Explanation:

Diffusing Update Algorithm (DUAL) is the algorithm for selecting and maintaining the best path to each remote network. DUAL tracks all the routes advertised by neighbors and selects routes based on feasible successors. It inserts lowest cost paths into the routing table (these routes are known as primary routes or successor routes) -> A is not correct.

EIGRP is still a distance-vector protocol, but has certain features that belong to link-state algorithms (like OSPF) than distance-vector algorithms. For example, EIGRP sends a partial routing table update, which includes just routes that have been changed, not the full routing table like distance-vector algorithms -> C is not correct.

The feasible successor route will become the primary route when its advertised distance is higher than the feasible distance of the successor route. The feasible successor route can be used in the event that the successor route goes down. Notice that the feasible successor route does not get installed in the routing table but is kept in the topology table as a backup route -> D is not correct.

“Support VLSM, route summarization, and routing update authentication” are the features of EIGRP -> B is correct.

When a route fails and has no feasible successor, EIGRP uses a distributed algorithm called Diffusing Update Algorithm (DUAL) to discover a replacement for a failed route. When a new route is found, DUAL adds it to the routing table -> E is correct.