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Exam Answers v3.x and v4.0
Options with "*" are correct answer
* TCP
IP
ICMP
UDP
HTTP
2 Which of the following would an administrator do to defend against a denial of service SYN flooding attack? (Choose two.)
Hide the source of incoming IP addresses.
* Decrease the connection timeout period.
Synchronize all host communication.
* Increase the connection queue size.
Flood the network with false SYN requests.
3 What is the purpose of Positive Acknowledgment and Retransmission (PAR)?
PAR allows the presentation layer to request that data be resent in a format the destination host can process.
PAR provides a mechanism for the receiving device to request that all segments be retransmitted if one segment is corrupt.
* PAR helps ensure that a number of data segments sent by one host are received by another host before additional data segments are sent.
PAR is used to renegotiate the window size during the synchronization process.
4 Which of the following describe types of port numbers that can be represented in the header of TCP and UDP segments? (Choose two.)
connectionless
* well-known
operational
* dynamic
static
5 Why is TCP considered a connection-oriented protocol?
It establishes a virtual connection between hosts using a two-way handshake.
It uses IP to guarantee delivery of packets between hosts.
* It requires hosts to go through a synchronization process prior to data transmission.
It creates a connection that depends on application layer protocols for error detection.
6 What is the purpose of using port numbers in the transport layer?
to identify the segment as being either TCP or UDP
to provide reliability during data transport
to identify the interface port number used by the router when forwarding data
* to track multiple conversations that occur between hosts
7 What does TCP use to ensure reliable delivery of data segments?
upper layer protocols
lower layer protocols
* sequence numbers
port numbers
8 Which authority has control over the assignment of port numbers for applications?
IEEE
* IANA
InterNIC
Software Developers Association
9 Which of the following describes how TCP adds reliability to communication? (Choose two.)
* Hosts using TCP set up virtual circuits at the beginning of the transmission using the three-way handshake.
Hosts using TCP set the error-checking frequency at the beginning of the transmission and maintain this frequency for the duration.
* The receiving host acknowledges that it has received the expected number of segments and requests additional data.
The receiving host acknowledges any incorrectly received data and requests retransmission of damaged or missing bytes.
10 Which address is dynamically assigned by the source host when forwarding data?
destination IP address
destination port number
default gateway address
source IP address
* source port number
11 Which of the following are functions of the TCP protocol? (Choose three.)
translation of data
* synchronization
path determination
* flow control
data representation
* reliability
12 Which transport layer unit of information places the port number in the header?
data
* segment
packet
frame
bit
13 What is the purpose of the three-way handshake that occurs between hosts using TCP as the transport layer protocol?
to determine the number of packets that can be sent before an acknowledgment is required
to allow a host to forward data to a router
* to establish a round trip connection between sender and receiver before data is transferred
to provide a mechanism for data encryption and compression
14 At which point in the transmission process are segments numbered?
when received
when reassembling
* before transmission
while negotiating window size
15 What type of segment and data is shown in the graphic?
a UDP segment carrying e-mail traffic
a TCP segment carrying FTP traffic
an IP segment carrying FTP traffic
a UDP segment carrying web traffic
* a TCP segment carrying web traffic
an IP segment carrying e-mail traffic
16 When a host receives a data segment, what allows the host to determine which application should receive the segment?
IP source address
IP destination address
PAR
sliding window
* port number
SYN packet
17 Which statement is true regarding the TCP protocol?
Flow control at the transport layer is provided by adding a sequence number to each segment.
* A sliding window allows for communicating devices to negotiate the amount of unacknowledged data that can be sent.
A window size of 1 would require a receiving device to send ACK 1 after the Segment 1 has been received.
TCP is used by sending hosts to segment large data files prior to transmission while IP is used by receiving host to reassemble the smaller segments.
18 What is used by both TCP and UDP when creating a segment?
IP address
MAC address
IPX address
* socket or port number
acknowledgment number
sequence number
19 What is used by UDP to determine if the data or header has been transferred without corruption?
lower layer protocols
* checksum
PAR
sliding window
acknowledgment and retransmission
IP
20 How are originating source port numbers assigned during the data encapsulation process?
assigned manually by the user when starting the application
* assigned dynamically by the source host
assigned by the routing protocol during the lookup process
assigned by the destination host during session negotiation
21 Which of the following protocols uses UDP for transport layer services?
SMTP
HTTP
* DNS
FTP
22 Which of the following determines the amount of data that can be sent without an acknowledgment when sending a TCP segment?
segment number
priority number
* window size
value in the length field
value in the port field
acknowledgment number
23 During the encapsulation process, in which order are the IP address, MAC address, and port number assigned when the router is establishing communication with the TFTP server?
IP address, MAC address, port number
MAC address, IP address, port number
* port number, IP address, MAC address
port number, MAC address, IP address
24 Which of the following describes a type of denial of service attack designed to exploit the normal function of the TCP three-way handshake?
* A host sends a packet with a spoofed source IP address.
A host sends a packet with an incorrect destination IP address.
A source sends a packet containing a garbled header.
A host sends an oversized packet that fills the memory buffers of the destination host.
A host sends a packet that contains a virus.
A host sends a packet that contains a worm.
V4.0
Options with highlight colours are correct answer
1. What action does a link-state router take immediately upon receipt of an LSP from a neighboring router?
o floods the LSP to neighbors
o calculates the SPF algorithm
o runs the Bellman-Ford algorithm
o computes the best path to the destination network
2. Why is it difficult for routing loops to occur in networks that use link-state routing?
o Each router builds a simple view of the network based on hop count.
o Routers flood the network with LSAs to discover routing loops.
o Each router builds a complete and synchronized view of the network.
o Routers use hold-down timers to prevent routing loops.
3. Refer to the exhibit. What kind of information would be seen in an LSP sent from router JAX to router ATL?
o hop count
o uptime of the route
o cost of the link
o a list of all the routing protocols in use
4. To achieve network convergence, what three steps does each link state router take? (Choose three.)
o use automatic summarization to reduce the size of routing tables
o build a Link State Packet (LSP) containing the state of each directly connected link
o flood the LSP to all neighbors, who then store all LSPs received in a database
o discover neighbors and establish adjacencies using the hello packet sent at regular intervals
o construct a complete map of the topology and compute the best path to each destination network
o use the DUAL FSM to select efficient, loop-free paths, and insert routes into the routing table
5. Refer to the exhibit. When Router D is configured to use a link-state routing protocol and is added to the
o It sends LSP packets to Routers B and C.
o It sends LSP packets to all routers in the network.
o It sends Hello packets to all routers in the network.
o It sends information about its directly connected neighbors to Routers A and E.
o It sends information about its directly connected neighbors to all routers in the network.
o It learns about its directly connected networks when its interfaces reach the up state.
6. A new network administrator is given the task of selecting an appropriate dynamic routing protocol for a
o RIP version 2
o IGRP
o EIGRP
o OSPF
o BGP
7. What two events will cause a link state router to send LSPs to all neighbors? (Choose two.)
o 30 second timer expires
o whenever the network topology changes
o immediately after the Bellman-Ford algorithm has run
o immediately after the DUAL FSM has built the topology database
o upon initial startup of router or routing protocol
8. What is the final step in the link state routing process?
o successors are placed into the routing table
o SPF computes best path to each destination network
o LSPs are flooded to all neighbors to converge the network
o DUAL algorithm is run to find best path to destination networks
9. Refer to the exhibit. What does JAX do with link-state packets from ORL?
o sends out its updated routing table to both ORL and BOS routers
o sends out the individual link-state packets out the interface connected to BOS
o queries BOS to see if it has a better route
o only adds it to the local routing table and performs no other actions
10. What two statements correctly describe the link state routing process? (Choose two.)
o each router in the area floods LSPs to all neighbors
o all routers in the area have identical link state databases
o LSPs use the reserved multicast address of 224.0.0.10 to reach neighbors
o routing loops are prevented by running the Diffusing Update Algorithm (DUAL)
o Reliable Transport Protocol (RTP) is the protocol used by for the delivery and reception of LSPs
11. Which database or table must be identical on all link-state routers within an area in order to construct an accurate
o routing table
o adjacency table
o link-state database
o neighbor table
o topology database
12. Refer to the exhibit. Which statement correctly describes the path traffic would take from the 10.0.0.0/24
o BOS -> ATL because this path is the least hops
o BOS -> ATL because this path is highest cost
o BOS -> ORL -> JAX -> ATL because this path is the lowest cost
o traffic would load balance across all links
13. What feature do modern link-state protocols provide to minimize processing and memory requirements?
o splitting routing topologies into smaller areas
o assigning lower process priorities to route calculations
o using update timers to restrict routing updates
o strict split horizon rules to reduce routing table entries
14. What speeds up convergence in a network using link-state routing?
o updates triggered by network changes
o updates sent at regular intervals
o updates sent only to directly connected neighbors
o updates that include complete routing tables
15. Which algorithm is run by link-state routing protocols to calculate the shortest path to destination networks?
o DUAL
o Dijkstra
o Bellman-Ford
o Diffie-Hellman
16. What are some of the advantages of using a link-state routing protocol instead of a distance vector routing
o The topology database eliminates the need for a routing table.
o Frequent periodic updates are sent to minimize the number of incorrect routes in the topological database.
o Routers have direct knowledge of all links in the network and how they are connected.
o After the inital LSA flooding, they generally require less bandwidth to communicate changes in a topology.**
o Link-state protocols require less router processor power than distance vector protocols.
17. Refer to the exhibit. If all routers and interfaces are configured to use a link-state routing protocol, from which
o A and E
o B and C
o A, B, C, and E
o C only
18. Which two routing protocols use Dijkstra’s shortest path first algorithm? (Choose two.)
o RIPv1
o RIPv2
o IS-IS
o BGP
o EIGRP
o OSPF
19. When are link-state packets sent to neighbors?
o every 30 seconds
o every 180 seconds
o after the holddown time expires
o when a link goes up or down
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