Introduction to Networks Version 6 – ITN Final Exam

Introduction to Networks (Version 6.00) – ITN Final Exam

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 DE packets 0

Correct Answer: C
Section: (none)
Explanation

Explanation/Reference:
Explanation:
If device A is sending data to device B across a Frame Relay infrastructure and one of the intermediate
Frame Relay switches encounters congestion, congestion being full buffers, over- subscribed port,
overloaded resources, etc, it will set the BECN bit on packets being returned to the sending device and the
FECN bit on the packets being sent to the receiving device.

QUESTION 2

Which command allows you to verify the encapsulation type (CISCO or IETF) for a Frame Relay link?

A.show frame-relay lmi
B.show frame-relay map
C.show frame-relay pvc
D.show interfaces serial

Correct Answer: B
Section: (none)
Explanation

Explanation/Reference:
Explanation:
When connecting Cisco devices with non-Cisco devices, you must use IETF4 encapsulation on both
devices. Check the encapsulation type on the Cisco device with the show frame-relay map exec command.

QUESTION 3

It has become necessary to configure an existing serial interface to accept a second Frame Relay virtual
circuit. Which of the following procedures are required to accomplish this task? (Choose three.)

A.Remove the IP address from the physical interface.
B.Encapsulate the physical interface with multipoint PPP.
C.Create the virtual interfaces with the interface command.
D.Configure each subinterface with its own IP address.
E.Disable split horizon to prevent routing loops between the subinterface networks.
F. Configure static Frame Relay map entries for each subinterface network.

Correct Answer: ACD
Section: (none)
Explanation

Explanation/Reference:
Explanation:
For multiple PVC’s on a single interface, you must use subinterfaces, with each subinterface configured for
each PVC. Each subinterface will then have its own IP address, and no IP address will be assigned to the main interface.

QUESTION 4

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.

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
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 5

Which two statements about using the CHAP authentication mechanism in a PPP link are true? (Choose two.)

A.CHAP uses a two-way handshake.
B.CHAP uses a three-way handshake.
C.CHAP authentication periodically occurs after link establishment.
D.CHAP authentication passwords are sent in plaintext.
E.CHAP authentication is performed only upon link establishment.
F. CHAP has no protection from playback attacks.

Correct Answer: BC
Section: (none)
Explanation

Explanation/Reference:
Explanation:
CHAP is an authentication scheme used by Point to Point Protocol (PPP) servers to validate the identity of
remote clients. CHAP periodically verifies the identity of the client by using a three-way handshake. This
happens at the time of establishing the initial link (LCP), and may happen again at any time afterwards. The
verification is based on a shared secret (such as the client user’s password).

QUESTION 6

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 Answer: C
Section: (none)
Explanation

Explanation/Reference:
Explanation:
DLCI-Data Link Connection Identifier Bits: The DLCI serves to identify the virtual connection so that the
receiving end knows which information connection a frame belongs to. Note that this
DLCI has only local significance. Frame Relay is strictly a Layer 2 protocol suite.

QUESTION 7

What is the result of issuing the frame-relay map ip 192.168.1.2 202 broadcast command?

A.defines the destination IP address that is used in all broadcast packets on DCLI 202
B.defines the source IP address that is used in all broadcast packets on DCLI 202
C.defines the DLCI on which packets from the 192.168.1.2 IP address are received
D.defines the DLCI that is used for all packets that are sent to the 192.168.1.2 IP address

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
Explanation:
This command identifies the DLCI that should be used for all packets destined to the 192.168.1.2 address.
In this case, DLCI 202 should be used.

QUESTION 8

Which PPP subprotocol negotiates authentication options?

A.NCP
B.ISDN
C.SLIP
D.LCP
E.DLCI

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
Explanation:
The PPP Link Control Protocol (LCP) is documented in RFC 1661. LPC
negotiates link and PPP parameters to dynamically configure the data link layer of a PPP connection.
Common LCP options include the PPP MRU, the authentication protocol, compression of PPP header
fields, callback, and multilink options.

QUESTION 9

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.

Correct Answer: BC
Section: (none)
Explanation

Explanation/Reference:
Explanation:
Subinterfaces are used for point to point frame relay connections, emulating virtual point to point leased
lines. Each subinterface requires a unique IP address/subnet. Remember, you can not assign multiple
interfaces in a router that belong to the same IP subnet.

QUESTION 10

What command is used to verify the DLCI destination address in a Frame Relay static configuration?

A.show frame-relay pvc
B.show frame-relay lmi
C.show frame-relay map
D.show frame relay end-to-end

Correct Answer: C
Section: (none)
Explanation

Explanation/Reference:
Explanation:
Sample “show frame-relay map” output:
R1#sh frame mapSerial0/0 (up): ip 10.4.4.1 dlci 401(0x191,0x6410), dynamic,broadcast,, status defined,
activeSerial0/0 (up): ip 10.4.4.3 dlci 403(0x193,0x6430), dynamic,broadcast,, status defined, activeSerial0/0
(up): ip 10.4.4.4 dlci 401(0x191,0x6410), static,CISCO, status defined, active

QUESTION 11

What is the purpose of Inverse ARP?

A.to map a known IP address to a MAC address
B.to map a known DLCI to a MAC address
C.to map a known MAC address to an IP address
D.to map a known DLCI to an IP address
E.to map a known IP address to a SPID
F. to map a known SPID to a MAC address

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
Explanation:
Dynamic address mapping relies on the Frame Relay Inverse Address Resolution Protocol (Inverse ARP),
defined by RFC 1293, to resolve a next hop network protocol (IP) address to a local DLCI value. The Frame Relay router sends out Inverse ARP requests on its Frame Relay PVC to discover the protocol address of the remote device connected to the Frame
Relay network. The responses to the Inverse ARP requests are used to populate an address-to-DLCI
mapping table on the Frame Relay router or access server. The router builds and maintains this address-toDLCI mapping table, which contains all resolved Inverse ARP requests, including both dynamic and static mapping entries.

QUESTION 12

Two routers named Atlanta and Brevard are connected via their serial interfaces as illustrated, but they are
unable to communicate. The Atlanta router is known to have the correct configuration.

Given the partial configurations, identify the fault on the Brevard router that is causing the lack of connectivity.

A.incompatible IP address
B.insufficient bandwidth
C.incorrect subnet mask
D.incompatible encapsulation
E.link reliability too low
F. IPCP closed

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
Explanation:
The correct explanation should be that the Atlanta router is usng HDLC while the Brevard is using PPP.
These need to match on both ends.

QUESTION 13

Refer to the exhibit. The company uses EIGRP as the routing protocol. What path will packets take from a
host on the 192.168.10.192/26 network to a host on the LAN attached to router R1?

A.The path of the packets will be R3 to R2 to R1.
B.The path of the packets will be R3 to R1 to R2.
C.The path of the packets will be both R3 to R2 to R1 AND R3 to R1.
D.The path of the packets will be R3 to R1.

Correct Answer: D
Section: (none)
Explanation

Explanation/Reference:
Explanation:
Host on the LAN attached to router R1 belongs to 192.168.10.64/26 subnet. From the output of the routing
table of R3 we learn this network can be reach via 192.168.10.9, which is an IP address in 192.168.10.8/30
network (the network between R1 & R3) -> packets destined for 192.168.10.64 will be routed from R3 -> R1 -> LAN on R1.

QUESTION 14

How does using the service password-encryption command on a router provide additional security?

A.by encrypting all passwords passing through the router
B.by encrypting passwords in the plain text configuration file
C.by requiring entry of encrypted passwords for access to the device
D.by configuring an MD5 encrypted key to be used by routing protocols to validate routing exchanges
E.by automatically suggesting encrypted passwords for use in configuring the router

Correct Answer: B
Section: (none)
Explanation

Explanation/Reference:
Explanation:
By using this command, all the (current and future) passwords are encrypted. This command is primarily useful for keeping unauthorized individuals from viewing your password in your configuration file

QUESTION 15

Refer to the exhibit. Switch port FastEthernet 0/24 on ALSwitch1 will be used to create an IEEE 802.1Qcompliant trunk to another switch. Based on the output shown, what is the reason the trunk does not form, even though the proper cabling has been attached?

A.VLANs have not been created yet.
B.An IP address must be configured for the port.
C.The port is currently configured for access mode.
D.The correct encapsulation type has not been configured.
E.The no shutdown command has not been entered for the port.

Correct Answer: C
Section: (none)
Explanation

Explanation/Reference:
Explanation:
According to the output shown the switchport (layer 2 Switching) is enabled and the port is in access mode.
To make a trunk link the port should configured as a trunk port, not an access port, by using the following
command: (Config-if)#switchport mode trunk

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