200-301 : Cisco Certified Network Associate (CCNA) : Part 15

200-301 : Cisco Certified Network Associate (CCNA) : Part 15

1. Which WAN switching technology is used with ISDN?

   • packet switching
   • virtual switching
   • circuit switching
   • cell switching
   Explanation:
   Circuit switching dynamically establishes a connection between a source and a destination. The connection cannot be used by other callers until the circuit is released. Circuit switching is the most common technique used with the public switched telephone network (PSTN) to make phone calls. During a call, a dedicated virtual circuit is temporarily established between the caller and receiver for the duration of the call. Once the caller or receiver hangs up the phone, the circuit is released and is made available for other users.

   Packet switching is a technique popularly used for transfer of data that is not delay sensitive and does not require real-time transfer rates from a sender to a receiver. Also unlike circuit switching which makes a fixed amount of bandwidth available for the connection (which may not be fully utilized) packet switching uses bandwidth more efficiently. With packet switching, the data is broken into labeled packets and is transmitted using packet-switching networks.

   Cell switching is used by Asynchronous Transfer Mode (ATM). ATM is an International Telecommunication Union-Telecommunications (ITU-T) standard for transmission of data, voice, or video traffic using a fixed size frame of 53 bytes, known as cells. Of these 53 bytes, the initial five bytes are header information and the remaining 48 bytes are the payload. These cells are transmitted over a path that may vary with each cell. It does not maintain a dedicated virtual circuit.

   The term “virtual switching” is incorrect because it is not a valid WAN switching technology.

   Objective:
   WAN Technologies
   Sub-Objective:
   Describe WAN access connectivity options

2. Which of the following are NOT valid IPv6 addresses? (Choose all that apply.)

   • 225.1.4.2
   • ::FFFF:10.2.4.1
   • ::
   • 2001:0:42:3:ff::1
   • fe80:2030:31:24
   • 2001:42:4:0:0:1:34:0
   • 2003:dead:bef:4dad:ab33:46:abab:62
   Explanation:
   The addresses 255.1.4.2 and fe80:2030:31:24 are not valid IPv6 addresses.

   225.1.4.2 is incorrect because it is an IPv4 multicast address. The address fe80:2030:31:24 is incorrect because it does not represent a 16-byte IPv6 address, with colons separating each 2-byte segment.

   IPv6 addresses are 16 bytes, or 128 bits in length. The following are valid IPv6 addresses.

   – ::FFFF:10.2.4.1 is an example of an IPv4-compatible IPv6 address, where the first 10 bytes (80 bits) of the address are set to 0 the next 2 bytes (16 bits) are set to FFFF and the last 32 bits are the IPv4 address
   – :: is the IPv6 “unspecified address.” It is a unicast address not assigned to any interface, and is used by a DHCP-dependent host prior to allocating a real IPv6 address.
   – 2001:0:42:3:ff::1 is a valid IP address, with the :: representing two segments (4 bytes) of – compressed zeros.
   – 2001:42:4:0:0:1:34:0 is a valid IP address, with only the leading zeros of each segment truncated.
   – 2003:dead:beef:4dad:ab33:46:abab:62 has 16 bytes, is divided correctly by colons into eight sections, utilizes the dropping of leading zeros in each section correctly, and uses the letters a-f in the three section that spell out dead beef 4 dad.

   Objective:
   Network Fundamentals
   Sub-Objective:
   Compare and contrast IPv6 address types

3. The conference room has a switch port available for use by the presenter during classes. You would like to prevent that port from hosting a hub or switch.

   Which of the following commands could be used to prevent that port from hosting a hub or switch?

   • switchport port-security maximum
   • switchport port-security mac address sticky
   • switchport port-security mac address
   • switchport port-security
   Explanation:
   The switchport port-security command would prevent the port from hosting a hub or switch. This command enables port security on an interface. It does not specify a maximum number of MAC addresses, but in the default is 1, therefore it would accomplish the goal.

   The switchport port-security maximum command alone could not be used to limit the number of MAC addresses allowed on the interface to 1. This command has no effect unless the switchport port-security command has been executed.

   The switchport port-security mac address sticky command would not prevent that port from hosting a hub or switch. This command is used to allow a port to dynamically learn the first MAC address it sees in the port, add it to the MAC address table and save it to the running configuration of the switch.

   The switchport port-security mac address command would not prevent that port from hosting a hub or switch. This command is used to manually assign a MAC address to a port as a secure address. When used in combination with the switchport port-security maximum command, the use of the port can not only be limited to one address at a time, but also limited to only a specific address. For example, the following set of commands would assure that only the device with the MAC address of 0018.cd33.46b3 will be able to connect to the port:

   Switch(config-if)#switchport port-security maximum 1
   Switch(config-if)#switchport port-security mac-address 0018.cd33.46b3

   Objective:
   Infrastructure Security
   Sub-Objective:
   Configure, verify, and troubleshoot port security

4. Given the following output, which statements can be determined to be true? (Choose three.)

   RouterA2# show ip ospf neighbor
   
   Neighbor ID Pri State Dead Time Address Interface
   192.168.23.2 1 FULL/BDR 00:00:29 10.24.4.2 FastEthernet1/0
   192.168.45.2 2 FULL/BDR 00:00:24 10.1.0.5 FastEthernet0/0
   192.168.85.1 1 FULL/- 00:00:33 10.6.4.10 Serial0/1
   192.168.90.3 1 FULL/DR 00:00:32 10.5.5.2 FastEthernet0/1
   192.168.67.3 1 FULL/DR 00:00:20 10.4.9.20 FastEthernet0/2
   192.168.90.1 1 FULL/BDR 00:00:23 10.5.5.4 FastEthernet0/1
   <<output omitted>>

   • This router is the DR for subnet 10.1.0.0.
   • The DR for the network connected to Fa0/0 has an interface priority greater than 2.
   • The DR for the network connected to Fa0/1 has a router ID of 10.5.5.2.
   • The DR for the serial subnet is 192.168.85.1.
   • This router is neither the DR nor the BDR for the Fa0/1 subnet.
   • RouterA2 is connected to more than one multi-access network.
   Explanation:
   The show ip ospf neighbor command displays a list of all OSPF routers with which you have established a neighbor relationship. The following describes the command output:
   – Neighbor ID: the Router ID (RID) of the neighboring router
   – Pri: the interface priority of the neighboring router, which is used to determine which router should serve the function of a Designated Router (DR)
   – State: the functional state of the neighboring router
   – Dead Time: the period that the router will wait to hear a Hello packet from this neighbor before declaring the neighbor down
   – Address: the IP address of the neighboring router on this subnet
   – Interface: the local interface over which the neighbor relationship (adjacency) was formed

   The output for neighbor 192.168.45.2 is as follows:

   192.168.45.2 2 FULL/BDR 00:00:24 10.1.0.5 FastEthernet0/0

   This indicates that the interface priority of neighbor 192.168.45.2 is 2. The default OSPF interface priority is 1, and the highest interface priority determines the designated router (DR) for a subnet. This same line reveals that this neighbor is currently the backup designated router (BDR) for this segment, which indicates that another router became the DR. It can be then be assumed that the DR router has an interface priority higher than 2. (The router serving the DR function is not present in the truncated sample output.)
   The output for the two neighbors discovered on F0/1 is as follows:

   192.168.90.3 1 FULL/DR 00:00:32 10.5.5.2 FastEthernet0/1
   192.168.90.1 1 FULL/BDR 00:00:23 10.5.5.4 FastEthernet0/1

   This output indicates that router 192.168.90.3 is the DR, and router 192.168.90.1 is the BDR for this network. Since there can only be one DR and BDR per segment, this indicates that the local router is neither the DR nor the BDR. (OSPF considers these DROther routers.)

   The fact that multiple DRs are listed in this output indicates that RouterA2 is connected to more than one multi-access segment, since each segment will elect a DR.

   It cannot be determined if this router is the DR for subnet 10.1.0.0. The output indicates that router 192.168.45.2 is the BDR for this network, but with the truncated output, it cannot be determined if this router is the DR.

   The DR for the network connected to Fa0/1 does not have a router ID of 10.5.5.2. The Address field of the show ip ospf neighbor command indicates the IP address of the neighbor’s interface, not the router ID of the neighbor.

   The DR for the serial subnet is not 192.168.85.1, since point-to-point serial interfaces do not elect DRs and BDRs. This is indicated by the output below:

   192.168.85.1 1 FULL/- 00:00:33 10.6.4.10 Serial0/1

   Objective:
   Routing Fundamentals
   Sub-Objective:
   Configure, verify, and troubleshoot single area and multi-area OSPFv2 for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub, virtual-link, and LSAs)

5. Which of the following are Wide Area Network (WAN) protocols? (Choose three.)

   • PPP
   • AAA
   • WEP
   • STP
   • HDLC
   • Frame Relay
   Explanation:
   Point-to-Point Protocol (PPP), High-Level Data Link Control (HDLC), and Frame Relay are WAN protocols.

   PPP is a WAN protocol is defined in Request for Comments (RFCs) 1332, 1661, and 2153. PPP works with asynchronous and synchronous serial interfaces as well as High-Speed Serial Interfaces (HSSI) and Integrated Services Digital Network (ISDN) interfaces (BRI and PRI). Some of the characteristics of PPP are:
   – Can be used over analog circuits
   – Can encapsulate several routed protocols, such as TCP/IP
   – Provides error correction
   – Should be used rather than HDLC when non-Cisco routers are involved, as it is implemented consistently among vendors
   – PPP authentication can be used between the routers to prevent unauthorized callers from establishing an ISDN circuit

   To change the encapsulation from the default of HDLC to PPP when connecting to a non-Cisco router, such as a Juniper, you would use the following command:

   router(config)#interface serial S0
   router(config-if)#encapsulation ppp

   HDLC is a WAN protocol used with synchronous and asynchronous connections. It defines the frame type and interaction between two devices at the Data Link layer.

   Frame Relay is a group of WAN protocols, including those from International Telecommunication Union (ITU-T) and American National Standards Institute (ANSI). Frame Relay defines interaction between the Frame Relay customer premises equipment (CPE) and the Frame Relay carrier switch. The connection across the carrier’s network is not defined by the Frame Relay standards. Most carriers, however, use Asynchronous Transfer Mode (ATM) as a transport to move Frame Relay frames between different sites.

   Authentication, Authorization, and Accounting (AAA) is incorrect because this is a scheme to monitor access control and activities on networked devices.

   Wired Equivalent Privacy (WEP) is a security scheme for wireless networks and therefore it is incorrect.

   Spanning Tree Protocol (STP) is for loop avoidance in redundant topologies. This option is incorrect because this protocol is used on Local Area Network (LAN).

   Objective:
   WAN Technologies
   Sub-Objective:
   Describe WAN access connectivity options

6. Which statement is supported by the following output?

   router# show ip protocols
   Routing Protocol is "eigrp 3"
   Sending updates every 90 seconds, next due in 24 seconds
   <<some output omitted>>
   EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
   EIGRP maximum hopcount 100
   EIGRP maximum metric variance 1
   Redistributing: eigrp 3
   Automatic network summarization is not in effect
   Maximum path: 4
   Routing for Networks:
   172.160.72.0
   192.168.14.0
   <<output omitted>>

   • EIGRP supports load-balancing over three equal-cost paths
   • EIGRP supports load-balancing over three unequal-cost paths
   • EIGRP supports load-balancing over four equal-cost paths
   • EIGRP supports load-balancing over four unequal-cost paths
   Explanation:
   The Maximum path: 4 output indicates that Enhanced Interior Gateway Routing Protocol (EIGRP) will support round-robin load-balancing over four equal-cost paths. This is a default setting, and is a true statement for most routing protocols (including RIP, OSPF and IS-IS). Equal-cost paths are different routes to the same destination network with identical metrics, as determined by the routing protocol. Most routing protocols allow this maximum to be raised up to 16 with the maximum-paths command.

   EIGRP has the additional benefit of allowing unequal cost load-balancing. With unequal cost load-balancing, the router can be configured to include less desirable (higher-metric) paths in the routing table. The router will then send a balanced percentage of traffic over both the best route and the less desirable paths, such as sending two packets over the best path plus one over a less desirable path. EIGRP will never perform unequal-cost load-balancing by default; it must be configured with a variance command. Therefore, you cannot state that EIGRP supports load-balancing over unequal-cost paths in this example.

   You cannot state that EIGRP will support load-balancing over three paths because the output displays the Maximum path: 4 value.

   Objective:
   Routing Fundamentals
   Sub-Objective:
   Configure, verify, and troubleshoot EIGRP for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub)

7. What command produced the preceding output?

   

   • show ip process
   • show ip route
   • show ip protocols
   • show ip routing process
   Explanation:
   The show ip protocols command is used to view the current state of active routing protocols. This command is issued from Privileged EXEC mode. It has the following syntax:

   Router# show ip protocols

   This command does not have any parameters.

   The output was not produced by the command show ip process or the show ip routing process. The show ip routing process and show ip process commands are incorrect because these are not valid Cisco IOS commands.

   The output was not produced by the command show ip route. The show ip route command is is used to view the current state of the routing table. An example of the output is shown below.

   

   Objective:
   Routing Fundamentals
   Sub-Objective:
   Interpret the components of routing table

8. You have two routers in your OSPF area 0. Router 1 is connected to Router 2 via its Serial 1 interface, and to your ISP via the Serial 0 interface. Router 1 is an ASBR.

   After your assistant configures a default route on Router 1, you discover that whenever either router receives packets destined for networks that are not in the routing tables, it causes traffic loops between the two routers.

   To troubleshoot, you execute the show run command on Router 1. Part of the output is shown below:

   <output omitted>
   IP route 0.0.0.0 0.0.0.0 serial 1
   Router ospf 1
   Network 192.168.5.0 0.0.0.255 area 0
   Default-information originate

   Which command or set of commands should you execute on Router 1 to stop the looping traffic while maintaining Router 2’s ability to send traffic to the Internet?

   • Execute the no default-information originate command.
   • Execute the no ip route 0.0.0.0 0.0.0.0 serial 1 command and then execute the ip route 0.0.0.0 0.0.0.0 serial 0 command.
   • Execute the default-information originate always command.
   • Execute the no network 192.168.5.0 area 0 command and then execute the network 192.168.5.0 255.255.255.0 area 0 command.
   Explanation:
   You should execute the no ip route 0.0.0.0 0.0.0.0 serial 1 command followed by the ip route 0.0.0.0 0.0.0.0 serial 0 command. The original configuration command was executed on the wrong interface on Router 1 by your assistant. It should be executed on Serial 0, which is the connection to the ISP. The show run command indicates that with the current configuration, if Router 2 receives a packet not in its table, it sends it to Router 1, and then Router 1 sends it back out on Serial 1. This redirects the packet back to Router 2, and the loop begins. By changing the configuration to Serial 0, Router 1 will start forwarding all traffic not in the routing table to the ISP.

   You should not execute the no default-information originate command. This command instructs Router 1 to NOT inject the default route into area 0, which is the desired behavior. Running this command would stop the loop, but would leave Router2 with no default route to send packets to the Internet.

   You should not execute the default-information originate always command. It will not change the existing looping behavior. The addition of the always parameter instructs Router 1 to inject a default route into area 0, even if one does not exist on Router 1. This is unnecessary, since Router 1 does have a default route configured, and will not change the existing looping behavior. To advertise a default route to other OSPF routers, you should run this command:

   Router1(config-router)#default information originate

   You should not execute the no network 192.168.5.0 area 0 command followed by the network 192.168.5.0 255.255.255.0 area 0 command. There is nothing wrong with the original network command. Also, the network 192.168.5.0 255.255.255.0 area 0 command uses an incorrect mask type. The mask must be in the wildcard format. Moreover, since it is incorrect, this will have the effect of disabling OSPF on the network connecting the two routers.

   Objective:
   Routing Fundamentals
   Sub-Objective:
   Configure, verify, and troubleshoot single area and multi-area OSPFv2 for IPv4 (excluding authentication, filtering, manual summarization, redistribution, stub, virtual-link, and LSAs)

9. Which type of switching process requires a switch to wait for the entire frame to be received before forwarding it to a destination port?

   • store and forward
   • cut-through
   • fragment free
   • frame-forward
   Explanation:
   The store and forward switching process requires a switch to wait until the entire frame is received before forwarding it to a destination port. The store and forward method increases latency as it buffers the entire frame and runs a Frame Check Sequence (FCS) before forwarding it to destination port. However, it ensures error-free frame forwarding because its filters all frame errors.

   The cut-through switching process does NOT require a switch to verify the FCS in a frame before forwarding it to the destination port. This type of internal switching method is faster than the store and forward process, but may forward error frames.

   The fragment-free switching process only waits to receive the first 64 bytes of the frame before forwarding it the destination port. Fragment-free internal switching assumes that if there is no error in the first 64 bytes of the data, the frame is error free. The assumption is based on the fact that if a frame suffers a collision, it occurs within the first 64 bytes of data. Fragment-free forwarding speed lies between that of store and forward and cut-through.

   The term frame-forward is not a valid internal switching process for Cisco switches.

   Objective:
   LAN Switching Fundamentals
   Sub-Objective:
   Describe and verify switching concepts

10. Which type of Dynamic Host Configuration Protocol (DHCP) transmission is used by a host to forward a DHCPDISCOVER packet to locate a DHCP server on the network?

    • unicast
    • broadcast
    • multicast
    • anycast
    Explanation:
    Hosts broadcast DHCPDISCOVER messages to locate a DHCP server. The following steps are followed during the allocation of the IP address dynamically using a DHCP server:
    – The client device broadcasts a DHCPDISCOVER message to locate a DHCP server.
    – The DHCP server replies with a DHCPOFFER unicast message with configuration parameters, such as an IP address, a MAC address, a domain name, and a lease for the IP address for the client device.
    – The client returns a DHCPREQUEST broadcast, which is a formal request for the offered IP address to the DHCP server.
    – The DHCP server replies to client device with DHCPACK unicast message, acknowledging the allocation of the IP address to this client device.

    Dynamic Host Configuration Protocol (DHCP) is an enhancement over Bootstrap Protocol (BOOTP) and is used to automate the distribution of IP address to clients from a central server. BOOTP protocol was also used to distribute IP addresses, but was inflexible to changes in the network.

    DHCP offers the following three advantages that also addressed the inflexibility of the BOOTP protocol:
    – Automatic allocation of permanent IP addresses
    – Automatic allocation of time bound (leased) IP addresses
    – Provision of assigning static IP address or defining a pool of reserved IP address

    DHCP does not use multicast messages.

    Anycast is a concept of IPv6 protocol and is not valid type used by DHCP.

    Objective:
    Infrastructure Services
    Sub-Objective:
    Configure and verify DHCP on a router (excluding static reservations)

11. DRAG DROP

    Click and drag the Open Systems Interconnection (OSI) layers to their corresponding functions on the right.

    

    

    Explanation:
    The following are the OSI layers along with their descriptions:
    – Application: Responsible for interacting directly with the application. It provides application services such as e-mail and File Transfer Protocol (FTP).
    – Physical: Consists of hardware for sending and receiving data on a carrier. The protocols which work at the Physical layer include Fast Ethernet, RS232, and Asynchronous Transfer Mode (ATM).
    – Transport: Responsible for error-free and sequential delivery of data. This layer is used to manage data transmission between devices, a process known as flow control. The Transport layer protocols are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).
    – Network: Used to define the network address or the Internet Protocol (IP) address, which is then used by the routers to make routing decisions.
    – The following are also OSI layers:
    – Presentation: Enables coding and conversion functions for application layer data. The formatting and encryption of data is done at this layer. The Presentation layer converts data into a format which is acceptable by the application layer.
    – Session: Used to create, manage, and terminate sessions between communicating nodes. The session layer handles the service requests and service responses, which take place between different applications.
    – Data Link: Ensures the reliable transmission of data across a network on the basis of Layer 2 addresses such as MAC addresses (Ethernet) or DLCIs (Frame Relay).

    Objective:
    Network Fundamentals
    Sub-Objective:
    Compare and contrast OSI and TCP/IP models

12. You need to cable the network shown below.

    

    Which of the following is the correct cable for each numbered link?

    • 1-crossover, 2-staight-through, 3-rollover, 4- crossover, 5-crossover
    • 1-straight-through, 2-staight-through, 3-rollover, 4- crossover, 5-crossover
    • 1-crossover, 2-crossover, 3-rollover, 4- crossover, 5-crossover
    • 1-rollover, 2-crossover, 3-crossover, 4- straight-through, 5-straight through
    Explanation:
    The correct cabling pattern is 1-rollover, 2-crossover, 3-crossover, 4- straight-through, 5-straight through. When selecting cables, the following rules apply:
    – Router to router- crossover
    – Router to switch- straight- through
    – Management station (PC) to router for console session- rolled cable
    – Switch to switch – crossover
    – PC to switch- straight through

    Objective:
    Network Fundamentals
    Sub-Objective:
    Select the appropriate cabling type based on implementation requirements

13. Examine the partial output of the show ip interface command below.

    

    What is the subnet broadcast address of the LAN connected to the router from which the command was executed?

    •  192.168.93.15
    • 192.168.93.255
    • 1.1.1.255
    • 1.1.1.127
    Explanation:
    In the output we can see there are two interfaces, a serial interface (which goes to another router) and a GigabitEthernet interface (the LAN interface). The LAN interface has an address of 192.168.93.1/28, which is a mask of 255.255.255.240. When this mask is used against the 192.168.93.0 classful network, it yields the following subnets:

    192.168.93.0
    192.168.93.16
    192.168.93.32
    192.168.93.48
    and so on, incrementing in intervals of 16 in the last octet.

    Since the LAN interface has an address of 192.168.93.1, the interface is in the 192.168.93.0/28 network. That networks broadcast address is the last address before the next subnet address of 192.168.93.16. Therefore, the broadcast address of the LAN connected to the router from which the command was executed is 192.168.93.15.

    The address 192.168.93.255 is not the broadcast address. If a standard 24-bit mask were used instead of the /28, this would be the broadcast address.

    The address 1.1.1.255 is the broadcast address of the network in which the Serial interface resides. The question asked for the LAN interface.

    The address 1.1.1.127 would be the broadcast address of the network in which the Serial interface resides if the mask used on the interface were 255.255.255.128. However, that is not the mask, and the question asked for the LAN interface.

    Objective:
    Network Fundamentals
    Sub-Objective:
    Configure, verify, and troubleshoot IPv4 addressing and subnetting

14. Which Cisco command will display the version and configuration data for Secure Shell (SSH)?

    • show ssh
    • show ip ssh
    • debug ssh
    • debug ip ssh
    Explanation:
    The show ip ssh command is used to display the version and configuration data for SSH on a Cisco router. The following is sample output of the show ip ssh command:

    router#show ip ssh
    SSH Enabled - version 1.5
    Authentication timeout: 120 secs; Authentication retries: 2

    This show ip ssh command output displays the enabled status of the SSH protocol, the retries parameter (configured at two attempts), and the timeout of 120 seconds.

    The following message will appear when the show ip ssh command is issued and SSH has been disabled:

    router# show ip ssh
    %SSH has not been enabled

    To enable SSH include the transport input SSH command when configuring authentication on a line. For example, the configuration of a Cisco network device to use SSH on incoming communications via the virtual terminal ports, with a specified password as shown from the partial output of the show run command is shown below:

    line vty 0 4
    password 7 030752180500
    login
    transport input ssh

    It is important to note the login command on the third line of the above ouput is critical for security. This command instructs the device to prompt for a username and password using SSH. If this line reads no login, SSH might be otherwise be correctly configured, but the device will never prompt for the username and password.

    The show ssh command will display the status of the SSH connections on the router The following is the sample output of the show ssh command:

    

    The debug ip ssh command is used to display debug messages for SSH.

    The debug ssh command is not a valid Cisco command.

    Objective:
    Infrastructure Management
    Sub-Objective:
    Use Cisco IOS tools to troubleshoot and resolve problems

15. You are the senior network administrator for a large corporation. Some new trainees have recently joined the network security team. You are educating them about denial-of-service (DoS) attacks and the risks posed to a network by such attacks.

    Which three are risks that a DoS attack poses to a network? (Choose three.)

    • Downtime and productivity loss
    • Spread of viruses
    • Revenue loss
    • Information theft
    • Spread of spyware
    Explanation:
    A DoS attack can result in network downtime and loss of productivity, revenue loss, and information theft.

    A DoS attack is an attack in which legitimate users are denied access to networks, systems, or resources. The potential risks posed by a DoS attack are as follows:
    – Downtime and productivity loss: A DoS attack causes downtime in the network, which ultimately results in loss of productivity for the organization.
    – Revenue loss: Organizations that use their Web sites for commerce or vital support services, such as search engines, can incur large revenue losses.
    – Information theft: DoS attacks can also be aimed at stealing important and confidential information from a network.
    – Malicious competition: An organization might launch DoS attacks against their competitors to damage their reputation.

    A few methods that can help minimize potential risks from DoS attacks are:
    – Using a firewall, which allows you to block or permit traffic entering into the network, can help to mitigate DoS attacks.
    – Computers vulnerable to attacks can be shifted to another location or a more secure LAN.
    – Intrusion Detection Systems (IDS), such as Network Intrusion Detection Systems (NIDS) and – Host Intrusion Detection Systems (HIDS), can be implemented to detect intrusive network or host activity, such as a DoS attack, and raise alerts when any such activity is detected.

    A DoS attack does not result in the spread of viruses because viruses are not spread by DoS attacks. Viruses are spread when the network is attacked by a virus or a Trojan horse.

    A DoS attack does not result in the spread of spyware. DoS attacks are mainly aimed at exhausting system resources so that legitimate users are denied access to networks, systems, or resources. Spyware is software installed on a computer without the knowledge of the user, and it gathers information about a person or organization. Spyware is generally downloaded through Web sites and e-mail messages.

    Objective:
    Infrastructure Security
    Sub-Objective:
    Configure, verify, and troubleshoot basic device hardening

16. Which of the following methods of tunneling Internet Protocol version 6 (IPv6) traffic through an IPv4 network increases protocol overhead because of IPv6 headers?

    • Protocol translation
    • IPv6 over dedicated WAN links
    • Dual-Stack Backbones
    • IPv6 over IPv4 tunnels
    Explanation:
    IPv6 over IPv4 tunnels is a method of tunneling IPv6 traffic through an IPv4 network that eliminates the need to create separate circuits to connect to the IPv6 networks. This model increases protocol overhead because of IPv6 headers.

    The following deployment models are available for IPv4 to IPv6 migration:
    – IPv6 over IPv4 tunnels: IPv6 traffic is encapsulated into IPv4 packets. Then these packets are transferred over IPv4 WAN. This model eliminates the need to create separate circuits to connect to the IPv6 networks. This model increases protocol overhead because of the IPv6 headers and requires both ends to be capable of both protocols.
    – Protocol translation: A method allowing an IPv6 host to communicate with an IPv4 host. This is accomplished with the help of Network Address Translation – Protocol Translation (NAT-PT) used to configure translation between IPv6 and IPv4 hosts. NAT-PT allows communication between IPv6 hosts and applications, and native IPv4 hosts and applications.
    – IPv6 over dedicated WAN links: A new deployment of IPv6 is created. In this model, IPv6 hierarchy, addressing, and protocols are used by all nodes. However, this model involves cost for creating IPv6 WAN circuits. This solution is not designed for LAN translation but rather translation over WAN links.
    – Dual-Stack Backbones: A hybrid model in which backbone routers have dual-stack functionality, which enables them to route both IPv4 and IPv6 packets. It is suitable for an enterprise that uses both IPv4 and IPv6 applications. Running IPv6 and IPv4 together in a network is known as dual-stack routing.

    Objective:
    Network Fundamentals
    Sub-Objective:
    Identify the appropriate IPv6 addressing scheme to satisfy addressing requirements in a LAN/WAN environment

17. Which of the following statements is NOT true of Cisco ACI?

    • It is a comprehensive SDN architecture.
    • It uses Cisco APIC as the central management system.
    • It provides policy driven automation support.
    • It decreases network visibility.
    Explanation:
    The Cisco ACI does not decrease network visibility. On the contrary, the Cisco Application Centric Infrastructure (ACI) increases network visibility. It is a policy-driven automaton solution that can keep the network inventory up-to-date automatically whenever a new device is added and provide a graphic representation at all times.

    ACI is a comprehensive SDN architecture that integrates physical and virtual environments under one policy model. It uses the Cisco Application Policy Infrastructure Controller (APIC) as the central management system.

    It provides policy driven automation support through a business-relevant application policy language.

    Objective:
    Infrastructure Management
    Sub-Objective:
    Describe network programmability in enterprise network architecture

18. You are the network administrator for your company. You want to use both IPv6 and IPv4 applications in the network. You also want to ensure that routers can route both IPv6 and IPv4 packets.

    Which deployment model should be implemented to accomplish the task?

    • IPv6 over IPv4 tunnels
    • IPv6 over dedicated Wide Area Network (WAN) links
    • Dual-Stack Backbones
    • Protocol translation
    Explanation:
    A dual-stack backbone deployment model should be used to accomplish the task in this scenario. When routers route both IPv6 and IPv4 packets, it is called dual stack routing or a dual-stack backbone.

    The following deployment models are available for IPv4 to IPv6 migration:
    – IPv6 over IPv4 tunnels: IPv6 traffic is encapsulated into IPv4 packets. Then these packets are transferred over an IPv4 WAN. This model eliminates the need to create separate circuits to connect to the IPv6 networks. This model increases protocol overhead because of the IPv6 headers and requires one end to be capable of both protocols
    – Protocol translation: A translation method of allowing an IPv6 host to communicate with an IPv4 host. This is accomplished with the help of Network Address Translation – Protocol Translation (NAT-PT) used to configure translation between IPv6 and IPv4 hosts. NAT-PT allows communication between IPv6 hosts and applications, and native IPv4 hosts and applications.
    – IPv6 over dedicated WAN links: A new deployment of IPv6 is created. In this model, IPv6 hierarchy, addressing, and protocols are used by all nodes. However, this model involves cost for creating IPv6 WAN circuits. This solution is not designed for LAN translation but rather translation over WAN links.
    – Dual-Stack Backbones: A hybrid model in which backbone routers have dual-stack functionality, which enables them to route both IPv4 and IPv6 packets. It is suitable for an enterprise that uses both IPv4 and IPv6 applications. Running IPv6 and IPv4 together in a network is known as dual-stack routing.

    Objective:
    Network Fundamentals
    Sub-Objective:
    Identify the appropriate IPv6 addressing scheme to satisfy addressing requirements in a LAN/WAN environment

19. Your assistant has been assigned the task of configuring one end of a WAN link between two offices. The link is a serial connection and the router on the other end is a non-Cisco router. The router in the other office has an IP address of 192.168.8.6/24. The connection will not come up, so you ask your assistant to show you the commands he configured on the Cisco router. The commands he executed are shown below.

    Ciscorouter(config)# interface serial0/0
    Ciscorouter(config-if)# ip address 192.168.8.5 255.255.255.0
    Ciscorouter(config-if)# no shut

    What command(s) should he run to correct the configuration?

    • Ciscorouter(config-if)# no ip address 192.168.8.5
      
      Ciscorouter(config-if)# ip address 192.168.8.10

    • Ciscorouter(config-if)# encapsulation ppp

    • Ciscorouter(config-if)# encapsulation ansi

    • Ciscorouter(config-if)# authentication chap

    Explanation:
    There are three encapsulation types available for a serial connection: High-Level Data Link Control (HDLC), Point-To-Point (PPP), and Frame Relay. HDLC is the default on Cisco routers and the form of HDLC used on a Cisco router is incompatible with routers from other vendors. Since the encapsulation command was not run, the router is set for HDLC. To correct this, you should execute the encapsulation ppp command. Frame Relay could also be used if the other router were running Frame Relay, since it also is an industry standard.

    The IP address does not need to be changed. It is currently set for 192.168.8.5/24. This is correct since it is in the same subnet as the IP address of the other end,192.168.8.6/24.

    The command authentication chap should not be run because the scenario does not indicate that authentication is configured on the other end. If it is set on one end, it must be set on the other as well.

    The command encapsulation ansi should not be run because ANSI is not an encapsulation type. It is an LMI type used in Frame Relay. The three LMI options available are Cisco, ANSI, and ITU.

    Objective:
    WAN Technologies
    Sub-Objective:
    Configure and verify PPP and MLPPP on WAN interfaces using local authentication

20. In which of the following IPv6 address assignment methods will the interface receive its IPv6 address from a process native to IPv6, and receive additional parameters from DHCP?

    • Stateless DHCPv6
    • Stateful DHCPv6
    • DHCPv6-PD
    • Stateless autoconfiguration
    Explanation:
    Stateless DHCPv6 uses a combination of processes to assign a configuration to an IPv6 interface. It uses Stateless Address Autoconfiguration (SAAC), a process native to IPv6, to assign an IPv6 address to the interface. It uses DHCPv6 to assign other parameters, such as the DNS server and NTP server.

    In stateful DHCPv6, the interface will receive the IPv6 address and all other parameters from the DHCP server.

    In DHCPv6 Prefix Designation (DHCPv6-PD), the device is assigned a set of IPv6 “subnets.” This assignment will consist of a set of IPv6 addresses in the same subnet (such as the address 2001:db8::/60) that the device can dynamically allocate to its interfaces.

    Objective:
    Network Fundamentals
    Sub-Objective:
    Configure and verify IPv6 Stateless Address Auto Configuration