Tài liệu Fravo Cisco 642-821 3.0 ppt

Reference: Building Cisco Remote Access Networks Ciscopress page 83 Q4.. Reference: Building Cisco Remote Access Networks Ciscopress page 21 Q5.. Reference: Building Cisco Remote Access

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Q1 When is ISDN BRI a viable option as a remote access solution?

A A mobile user that needs access to the central site while traveling

B A branch office needs to connect to a mobile user

C A remote site with sporadic traffic needs to connect to central site

D A branch office requires at least 300kbps bandwidth to the central site

Answer: C

Explanation: Basic Rate Interface (BRI) is an Integrated Systems Digital Network (ISDN) interface, and it consists of two B channels (B1 and B2) and one D channel The B channels are used to transfer data, voice, and video The D channel controls the B channels

ISDN uses the D channel to carry signal information ISDN can also use the D

channel in a BRI to carry X.25 packets The D channel has a capacity of 16 kbps, and the X.25 over D channel can utilize up to 9.6 kbps When this feature is configured, a separate X.25-over-D-channel logical interface is created You can set its parameters without disrupting the original ISDN interface configuration The original BRI

interface will continue to represent the D, B1, and B2 channels

Because some end-user equipment uses static terminal endpoint identifiers (TEIs) to access this feature, static TEIs are supported The dialer understands the X.25-over-D-channel calls and initiates them on a new interface

X.25 traffic over the D channel can be used as a primary interface where

low-volume, sporadic interactive traffic is the normal mode of operation Supported traffic includes IPX, AppleTalk, transparent bridging, XNS, DECnet, and IP

This feature is not available on the ISDN Primary Rate Interface (PRI)

Reference:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1826/products_configuration_guide_chapter09186a00800d9b8a.html

Q2 Which statement is true regarding the ADSL (G.Lite G.922.2) standard?

A Signals cannot be carried on the same wire as POTS signals

B It offers equal bandwidth for upstream and downstream data traffic

C It was developed specifically for the consumer market segment requiring higher download speeds

D It has limited operating range of less than 4,500 feet

Answer: C

Explanation: Asymmetric Digital Subscriber Line (ADSL) is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream Downstream rates range from 1.5 to 9 Mbps, whereas upstream bandwidth ranges from 16 to 640 kbps ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair

Reference:

http://www.cisco.com/en/US/tech/tk175/tk15/tech_protocol_family_home.html

Q3 Which command will allow a router to attempt to discover the modem to which it

is attached?

A modem autoconfigure discovery

B modem discovery autoconfigure

C modem autoconfigure type discovery

D modem discovery type autoconfigure

Answer: A

Explanation: If no modem is specified for a particular line and you have provided the modem autoconfigure discovery command, the access server attempts to

autodiscover the type of modem to which it is attached The access server

determines the type of modem by sending AT commands to the modem and

evaluating the response

Reference: Building Cisco Remote Access Networks (Ciscopress) page 83

Q4 Which user requirement is best served by an access server?

A Mobile sales force requiring dial-in access

B Mobile sales force requiring dedicated connection

C Corporate staff requiring access to web-bases applications

D Corporate staff requiring access to applications on corporate systems

Answer: A

Explanation: A router act access server, which is a concentration point for dial-in and dial-out calls Mobile users, for example, can call into an access server at a Central site to access their messages

Reference: Building Cisco Remote Access Networks (Ciscopress) page 21

Q5 Which feature will cache routes learned by dynamic routing protocols, enabling their use over DDR connections?

need to configure the routes to be redistributed to a dynamic routing protocol at the core side

Reference: Building Cisco Remote Access Networks (Ciscopress) page 190

Q6 The network administrator enables Frame Relay traffic shaping and configures a CIR of 64kbps Using 125ms time interval, what will be the value of the committed burst (Bc)

Reference: Building Cisco Remote Access Networks (Ciscopress) page 352

Q7 Drag the queuing method from the list on the right to the appropriate description

on the right (Note: not all options will be used.)

Answer:

Explanation:

Custom queuing – reserves a certain percentage of bandwidth for each

specified class of traffic

Weighted fair queuing – prioritizes interactive traffics over file transfers to

ensure satisfactory response time for common user applications

Basic queuing – No such thing

Priority queuing – ensures the timely delivery of a specific protocol or

type of traffic because that traffic is transmitted before all others

Reference: Building Cisco Remote Access Networks (Ciscopress) page 399

Q9 Which of the following are examples of DTE devices? (Choose three.)

Explanation: Data terminal equipment (DTE) are end devices such as PCs,

workstations, routers, and mainframe computers

Reference: Building Cisco Remote Access Networks (Ciscopress) page 57

Q10 Based on the configuration shown, what is the CIR of interface Serial0/0 300?

To specify the incoming or outgoing committed information rate (CIR)for a Frame

Relay virtual circuit, use the frame-relay cir map-class configuration command

To reset the CIR to the default, use the no form of this command

frame-relay cir {in | out} bps

no frame-relay cir {in | out} bps

Reference:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1824/products_command_reference_chapter09186a0080087bcd.html#xtocid106829

Q11 Which three are responsible of IKE in the IPSec protocol? (Choose three.)

A Negotiating protocol parameters

B Packet encryption

C Exchanging public keys

D Integrity checking user hashes

E Authenticating both sides of a connection

F Implementing tunnel mode

Answer: A, C, E

Explanation: IKE is a protocol used by IPSec for completion of Phase 1 IKE

negotiates and assigns SAs for each IPSec peer, which provide a secure channel for the negotiation of the IPSec SAs in Phase 2 IKE provides the following benefits:

both peers

• Lets you specify a lifetime for the IKE SAs

• Allows IPSec to provide anti-replay services

Reference:

http://www.cisco.com/en/US/products/sw/secursw/ps2120/products_configuration_guide_chapter09186a008017278c.html#39982

Q12 What are four PPP options that are negotiated using LCP? (Choose four.)

Reference: Building Cisco Remote Access Networks (Ciscopress) page 111

Q13 Under which circumstance would use of Kerberos authentication system be required, instead of TACACS+ or RADIUS?

A Authentication, authorization and accounting need to use the a single database

B Multiple level of authorization need to be applied to various router commands

C DES encrypted authentication is required

D The usage of various router functions needs to be accounted for by user name

Answer: C

Explanation: Kerberos is a client-server based secret-key network authentication method that uses a trusted Kerberos server to verify secure access to both services and users In Kerberos, this trusted server is called the key distribution center

(KDC) The KDC issues tickets to validate users and services A ticket is a temporary set of electronic credentials that verify the identity of a client for a particular service These tickets have a limited life span and can be used in place of the standard user password authentication mechanism if a service trusts the Kerberos server from which the ticket was issued If the standard user password method is used, Kerberos encrypts user passwords into the tickets, ensuring that passwords are not sent on the network in clear text When you use Kerberos, passwords are not stored on any machine, except for the Kerberos server, for more than a few seconds Kerberos also guards against intruders who might pick up the encrypted tickets from the network Reference:

http://www.cisco.com/en/US/tech/tk583/tk642/technologies_tech_note09186a0080094ea4.shtml

Q14 Frame Relay describes the interconnection process between which two types of equipment?

A DTE and DTE

B DCE and DCE

C CPE and DTE

D CPE and DCE

Answer: D

Explanation: Frame relay defines the interconnection process between your customer premises equipment (CPE- also known as data terminal equipment [DTE]) such as a router, and the service provider’s local access-switching equipment (known as data communications equipment [DCE])

Reference: Building Cisco Remote Access Networks (Ciscopress) page 340

Q15 Given the following debug output, which two statements are true? (Choose two.)

1d16h: %LINK-3- UPDPDOWN: Interface Serial3/0, changed state to up

*Mar 2 16:52:15.297: Se3/0 PPP: Treating connection as a dedicated line

*Mar 2 16:52:15.441: Se3/0 PPP: Phase is AUTHENTICATING, by this end

*Mar 2 16:52:15.445: Se3/0 CHAP: O CHALLENGE id 7 len 29 from

“NAS1”

A The user is authenticating with the privileged mode password “NAS1”

B This is a connection attempt to an async port

C The connection is established on serial interface 3/0

D The client is attempting to setup a Serial Line Internet Protocol connection

E The user is authenticating using CHAP

Answer: C, E

Explanation: When using Chap authentication, the access server sends a challenge message to the remote node after the ppp link is established The remote node responds with a value calculated by using a one-way hash function The access server (NAS1) checks the reponse against its own calculation of the expected hash value

Reference: Building Cisco Remote Access Networks (Ciscopress) page 115

Q16 Which of the following terminals can be connected to an ISDN line? (Choose two.)

Terminal equipment 1(TE1) - Designates a device that is compatible with the

ISDN network A TE1 connects to a Network Termination of either Type 1 or Type 2, such as a digital telephone, a router with ISDN interface, or digital facsimile

equipment

Terminal equipment 2(TE2) - Designates a device that is not compatible with the

ISDN and requires a terminal adapter, such as terminals with X.21, EIA/TIA-232, or X.25 interfaces or a router without a ISDN interface (AGS= and so on)

Terminal adapter – converts standard electrical signals into the form used by

ISDN, so that non-ISDN devices can connect to the ISDN network

Reference: Building Cisco Remote Access Networks (Ciscopress) page 171

Q17 Serial0 on a router is configured with the command encapsulation frame -relay What can cause the output from the show interface command to indicate:

Serial0 is up, line protocol is down?

A No carrier signal

B IP subnet mismatch

C LAPF state, down

D LMI type mismatch

E No IP address configured

Answer: D

Explanation:

"Serial0 is up, line protocol is down"

This line in the output means that the router is getting a carrier signal from the CSU/DSU or modem Check to make sure the Frame Relay provider has activated their port and that your Local Management Interface (LMI) settings match

Generally, the Frame Relay switch ignores the data terminal equipment (DTE) unless

it sees the correct LMI (use Cisco's default to "cisco" LMI) Check to make sure the Cisco router is transmitting data You will most likely need to check the line integrity using loop tests at various locations beginning with the local CSU and working your way out until you get to the provider's Frame Relay switch

Reference:

http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml#serialupdown

Q18 Given the configuration:

access-list 101 permit ip any any

access-list 101 deny tcp any any eq ftp

dialer-list 2 protocol ip list 101

Which two statements about the configuration are true with respect to FTP traffic and DDR? (Choose two.)

A FTP traffic will be forwarded

B FTP traffic will not be forwarded

C FTP will cause the line to come up

D Since FTP uses two sockets, both must be defined to prevent packet forwarding Answer: B, C

Explanation:

Access-list 101 deny tcp any any eq ftp - will stop any ftp traffic to any host dialer-list 2 protocol ip list 101 – command is used to configure dial-on-demand

calls that will initiate a connection

Reference: Building Cisco Remote Access Networks (Ciscopress) page 187 - 194

Q19 Drag and drop the ISDN in the options column to the related term in the target column

Answer:

Explanation:

U interface – defines the two-wire interface between the NT and the ISDN cloud

TE1 – designates a device that is compatible with the ISDN

network

R interface – defines the interface between the TA and an attached

non-ISDN device (TE2)

S/T interface – is a four-wire interface (TX and RX)

TE2 – designates a device that is not compatible with ISDN and

requires a terminal adapter

Reference: Building Cisco Remote Access Networks (Ciscopress) page 171-173

Q20 What occurs when there is no longer a signal on the DTR?

A The CD tells the DTE that a DCE-to-DCE connection has been established

B The DTE issues a RTS to the DCE enabling communication

C The DCE terminates its connection with the remote modem

D The DTE applies voltage on pin 20 to alert the DCE that it is connected and available to receive data

Answer: C

Explanation: Either the DTE device or the DCE device may signal for the connection

to be terminated The signals that are used for this function are DTR from the DTE or the modem recognizing the loss of the CD signal

Reference: Building Cisco Remote Access Networks (Ciscopress) page 60

Q21 Which statements are true regarding the command telnet 10.10.30.4 2009? (Choose two.)

A It is used to reverse Telnet connection

B It is used to Telnet to port 2009 on a specific computer

C A modem is connected to line 9

D It specified a BRI connection to be used for Telnet

Answer: B, C

Explanation:

B: Telnet protocol uses 2000 base TCP port for individual lines

C: TTY lines 1 through 24 directly connect to modems 1/0 through 1/23, which are installed in the first chassis slot in this example The TTY lines 25 through 48 directly connect to modems 2/0 through 2/23, which are installed in the second slot

Reference: Building Cisco Remote Access Networks (Ciscopress) page 70

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca657.html

Q22 A small remote site requires a low cost, T1 speed connection to make secure file transfers to a central site located several hundred miles away Which connection type will meet the requirements of this application?

Frame Relay – Medium control, shared bandwidth, medium-cost enterprise

backbones It uses the services of many different Physical layer facilities at speeds that typically range from 56 Kbps up to 2 Mbps

Reference: Building Cisco Remote Access Networks (Ciscopress) page 27 + 340

Q23 Which three of the following ro uter IOS commands defines “interesting” traffic for only one host using dial on command routing (DDR) (Choose three.)

A RTA(config)#dialer-list 1 protocol ip permit 10.1.1.1

B RTA(config)#access-list 2 permit host 192.168.1.12

C RTA(config-if)#dialer-group 1

D RTA(config)#dialer-group 2

E RTA(config)#dialer-list 1 protocol ip list 2

F RTA(config-if)#dialer-list 2 protocol ip permit

Answer: A, B, E

Explanation: Define what constitutes interesting traffic by using the dialer-list

command

The access-list command specifies interesting traffic that initiates a DDR call

These commands are assigned on the global configuration line

The dialer-group command needs to be assigned to the interface responsible for

initiating the call

Reference: Building Cisco Remote Access Networks (Ciscopress) page 188

Q24 When using PPPoE to communicate over a DSL service connection, which process must be performed by the host to establish a PPPoE SESSION_ID?

A A Bootp process to request a configuration and session ID

B A Discovery process to identify a PPPoE server and request a session ID

C A DHCP request process to request and IP address and session ID

D A RARP request process to request a MAC address and session ID

Answer: B

Explanation: When a host wishes to initiate a PPPoE session, it must first perform discovery to identify the Ethernet MAC address of the peer and establish a PPPOE SESSION_ID Although PPP defines a peer-to-peer relationship, discovery is

inherently a client/server relationship In the discovery process, a host (the client) discovers an access concentrator (the server) Based on the network topology, there may be more than one access concentrator that the host can communicate with The Discovery Stage allows the host to discover all access concentrators and then select one When discovery is completed, both the host and the selected access

concentrator have the information they will use to build their point-to-point

connection over Ethernet

Reference:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a008007fe7d.html

Q25 What are the three possible states of a Frame Relay permanent virtual circuit (PVC)?

Q26 Which command will change the specified Frame Relay encapsulation for a specific PVC on an interface?

A no frame -relay encapsulation ietf

B no frame-relay encapsulation cisco

C encapsulation frame-relay ietf

D frame-relay map ip 10.160.2.1 100 broadcast ietf

Answer: D

Explanation: The default encapsulation, which is Cisco, is applied to all the VCs available on that serial interface If most destinations use the Cisco encapsulation,

but one destination requires the IETF, you would specify, under the interface, the general encapsulation to be used by most destinations Because the default

encapsulation is Cisco, you would specify the exception using the frame-relay map

command

Reference: Building Cisco Remote Access Networks (Ciscopress) page 347

Q27 Which six AAA accounting types will a TACACS+/RADIUS server record?

A Network, interface, exec, protocol, system, and resource

B Resource, interface, connection, system, command, and network

C Command, system, exec, network, connection, and resource

D Connection, protocol, system, network, command, and resource

E Crypto, system, network, protocol, command, and resource

Answer: C

Explanation:

system - Enables accounting for all system-level events not associated with users,

such as reloads

network - Enables accounting for all network-related requests, including SLIP, PPP,

PPP network control protocols, and ARAP

connection - Enables accounting for outbound Telnet and rlogin

exec - Enables accounting for EXEC processes (user shells)

command - level Enables accounting for all commands at the specified privilege

level

Reference:

http://www.cisco.com/en/US/products/sw/secursw/ps4911/products_user_guide_chapter09186a00800eb6ce.html

Q28 You are the network administrator at your company A boarding supply store's manager within the company needs access from home to the store's internal

network You are asked to their router enabling it to accept asynchronous

connections through a modem It is your task to configure the serial port S0/1 for asynchronous communication and to enable a reverse telnet session to the attached modem No other router or modem configuration is necessary at this time Your task

is complete when you are able to reverse telnet to the modem and issue an AT command to begin modem configuration

Task steps:

• Set the line password to "cisco"

• Configure the line to allow for both incoming and outgoing calls

• Allow all protocols for incoming connections on the line

• Reverse telnet to the modem

To c onfigure the router clock on a host icon that is connected to a router by a serial console cable

Typical circuit switched connections are as follows:

ISDN Primary rate Interface (PRI)

Reference: Building Cisco Remote Access Networks (Ciscopress) page 20 21