Cisco 100-101 Online Practice Questions and Exam Preparation

Cisco 100-101 Online Questions & Answers

• Question 11:

  From which of the following attacks can Message Authentication Code (MAC) shield your network?

  A. DoS
  B. DDoS
  C. spoofing
  D. SYN floods
  C. spoofing

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  Message Authentication Code (MAC) can shield your network from spoofing attacks. Spoofing, also known as masquerading, is a popular trick in which an attacker intercepts a network packet, replaces the source address of the packets header with the address of the authorized host, and reinserts fake information which is sent to the receiver. This type of attack involves modifying packet contents. MAC can prevent this type of attack and ensure data integrity by ensuring that no data has changed. MAC also protects against frequency analysis, sequence manipulation, and ciphertext-only attacks. MAC is a secure message digest that requires a secret key shared by the sender and receiver, making it impossible for sniffers to change both the data and the MAC as the receiver can detect the changes. A denial-of-service (DoS) attack floods the target system with unwanted requests, causing the loss of service to users. One form of this attack generates a flood of packets requesting a TCP connection with the target, tying up all resources and making the target unable to service other requests. MAC does not prevent DoS attacks. Stateful packet filtering is the most common defense against a DoS attack. A Distributed Denial of Service attack (DDoS) occurs when multiple systems are used to flood the network and tax the resources of the target system. Various intrusion detection systems, utilizing stateful packet filtering, can protect against DDoS attacks. In a SYN flood attack, the attacker floods the target with spoofed IP packets and causes it to either freeze or crash. A SYN flood attack is a type of denial of service attack that exploits the buffers of a device that accept incoming connections and therefore cannot be prevented by MAC. Common defenses against a SYN flood attack include filtering, reducing the SYN- RECEIVED timer, and implementing SYN cache or SYN cookies.

• Question 12:

  Which three approaches can be used while migrating from an IPv4 addressing scheme to an IPv6 scheme? (Choose three)

  A. static mapping of IPv4 address to IPv6 addresses
  B. configuring IPv4 tunnels between IPv6 islands
  C. use DHCPv6 to map IPv4 addresses to IPv6 addresses
  D. use proxying and translation (NAT-PT) to translate IPv6 packets into IPv4 packets
  E. configure IPv6 directly
  F. enable dual-stack routing
  B. configuring IPv4 tunnels between IPv6 islands
  D. use proxying and translation (NAT-PT) to translate IPv6 packets into IPv4 packets
  F. enable dual-stack routing

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  http://www.opus1.com/ipv6/howdoitransitiontoipv6.html Connecting IPv6 islands with tunnels An IPv6 island is a network made of IPv6 links directly connected by IPv6 routers. In the early days of IPv6 deployment, there are many IPv6

  islands. IPv6 in IPv4 tunnels are used to connect those islands together. In each island, one (or more) dual stack routers are designated to encapsulate and decapsulate IPv6 packets within IPv4 packets. Different mechanisms have been

  developed to manage tunnels: automatic tunnels3, configured tunnels3, tunnel brokers3, 6over43, 6to43,...

  Reference 2:

  http://www.petri.co.il/ipv6-transition.htm

  Network Address Translation - Protocol Translation (NAT-PT) The NAT-PT method enables the ability to either statically or dynamically configure a translation of a IPv4 network address into an IPv6 network address and vice versa. For those

  familiar with more typically NAT implementations, the operation is very similar but includes a protocol translation function. NAT-PT also ties in an Application Layer Gateway (ALG) functionality that converts Domain Name System (DNS)

  mappings between protocols.

  Dual Stack

  The simplest approach when transitioning to IPv6 is to run IPv6 on all of the devices that are currently running IPv4. If this is something that is possible within the organizational network, it is very easy to implement.

  However, for many organizations, IPv6 is not supported on all of the IPv4 devices; in these situations other methods must be considered.

• Question 13:

  Which one of the following IP addresses is the last valid host in the subnet using mask 255.255.255.224?

  A. 192.168.2.63
  B. 192.168.2.62
  C. 192.168.2.61
  D. 192.168.2.60
  E. 192.168.2.32
  B. 192.168.2.62

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  With the 224 there are 8 networks with increments of 32 One of these is 32 33 62 63 where 63 is broadcast so 62 is last valid host out of given choices.

• Question 14:

  A network administrator is trying to add a new router into an established OSPF network. The networks attached to the new router do not appear in the routing tables of the other OSPF routers. Given the information in the partial configuration shown below, what configuration error is causing this problem? Router(config)# router ospf 1 Router(config-router)# network 10.0.0.0 255.0.0.0 area 0

  A. The process id is configured improperly.
  B. The OSPF area is configured improperly.
  C. The network wildcard mask is configured improperly.
  D. The network number is configured improperly.
  E. The AS is configured improperly.
  F. The network subnet mask is configured improperly.
  C. The network wildcard mask is configured improperly.

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  When configuring OSPF, the mask used for the network statement is a wildcard mask similar to an access list. In this specific example, the correct syntax would have been "network 10.0.0.0 0.0.0.255 area 0."

• Question 15:

  Refer to the topology and switching table shown in the graphic.

  

  Host B sends a frame to Host C. What will the switch do with the frame?

  A. Drop the frame
  B. Send the frame out all ports except port 0/2
  C. Return the frame to Host B
  D. Send an ARP request for Host C
  E. Send an ICMP Host Unreachable message to Host B
  F. Record the destination MAC address in the switching table and send the frame directly to Host C
  B. Send the frame out all ports except port 0/2

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• Question 16:

  A router has learned three possible routes that could be used to reach a destination network. One route is from EIGRP and has a composite metric of 20514560. Another route is from OSPF with a metric of 782. The last is from RIPv2 and has a metric of 4. Which route or routes will the router install in the routing table?

  A. the OSPF route
  B. the EIGRP route
  C. the RIPv2 route
  D. all three routes
  E. the OSPF and RIPv2 routes
  B. the EIGRP route

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  When one route is advertised by more than one routing protocol, the router will choose to use the routing protocol which has lowest Administrative Distance. The Administrative Distances of popular routing protocols are listed below:

  

• Question 17:

  Which characteristics are representative of a link-state routing protocol? (Choose three.)

  A. provides common view of entire topology
  B. exchanges routing tables with neighbors
  C. calculates shortest path
  D. utilizes event-triggered updates
  E. utilizes frequent periodic updates
  A. provides common view of entire topology
  C. calculates shortest path
  D. utilizes event-triggered updates

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  Each of routers running link-state routing protocol learns paths to all the destinations in its "area" so we can say although it is a bit unclear.

  Link-state routing protocols generate routing updates only (not the whole routing table) when a change occurs in the network topology so

  Link-state routing protocol like OSPF uses Dijkstra algorithm to calculate the shortest path -> . Unlike Distance vector routing protocol (which utilizes frequent periodic updates), link-state routing protocol utilizes event-triggered updates (only

  sends update when a change occurs) ->

• Question 18:

  The internetwork infrastructure of company XYZ consists of a single OSPF area as shown in the graphic. There is concern that a lack of router resources is impeding internetwork performance. As part of examining the router resources, the OSPF DRs need to be known. All the router OSPF priorities are at the default and the router IDs are shown with each router.

  

  Which routers are likely to have been elected as DR? (Choose two.)

  A. Corp-1
  B. Corp-2
  C. Corp-3
  D. Corp-4
  E. Branch-1
  F. Branch-2
  D. Corp-4
  F. Branch-2

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  There are 2 segments on the topology above which are separated by Corp-3 router. Each segment will have a DR so we have 2 DRs.

  To select which router will become DR they will compare their router-IDs. The router with highest (best) router-ID will become DR. The router-ID is chosen in the order below:

  + The highest IP address assigned to a loopback (logical) interface. + If a loopback interface is not defined, the highest IP address of all active router's physical interfaces will be chosen.

  In this question, the IP addresses of loopback interfaces are not mentioned so we will consider IP addresses of all active router's physical interfaces. Router Corp-4 (10.1.40.40) and Branch-2 (10.2.20.20) have highest "active" IP addresses so they will become DRs.

• Question 19:

  What is the best practice when assigning IP addresses in a small office of six hosts?

  A. Use a DHCP server that is located at the headquarters.
  B. Use a DHCP server that is located at the branch office.
  C. Assign the addresses by using the local CDP protocol.
  D. Assign the addresses statically on each node.
  D. Assign the addresses statically on each node.

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  Its best to use static addressing scheme where the number of systems is manageable rather than use dynamic protocol as it is easy to operate and manage.

• Question 20:

  Refer to the exhibit.

  

  What must be configured to establish a successful connection from Host A to switch SW-A through router RT-A?

  A. VLAN 1 on RT-A
  B. IP routing on SW-A
  C. default gateway on SW-A
  D. crossover cable connecting SW-A and RT-A
  C. default gateway on SW-A

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  In order for the switch to reach networks that are not local, such as networks attached to different interfaces of the router, it will need to set its default gateway to be the IP address of the attached router.