CS 6250 Computer Networks Exam 2
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. In the context of computer networks, which statement most
accurately describes the primary purpose of the Internet Protocol (IP)
layer in the TCP/IP architecture?
A. To guarantee reliable, ordered delivery of application data between
processes
B. To provide end-to-end encryption for all application traffic
C. To provide logical addressing and route packets across interconnected
networks
D. To establish persistent sessions between application processes
The IP layer is responsible for logical addressing and forwarding packets
between networks. Reliability, ordering, and process-to-process
communication are primarily provided by higher-layer protocols such as
TCP.
2. A router receives an IP packet whose destination address does not
belong to any directly connected network. What does the router
normally do to determine where the packet should be forwarded?
A. It broadcasts the packet to every neighboring router
B. It sends the packet to the application layer for interpretation
,C. It consults its forwarding table and selects the best matching route
D. It changes the destination IP address to the router's own address
Routers use forwarding tables to determine the appropriate outgoing
interface and next hop. The longest-prefix-match principle is commonly
used when multiple routes match a destination address.
3. Which property distinguishes a forwarding table from a routing table
in a typical network router?
A. The forwarding table contains only application-layer information
B. The routing table is used exclusively by Ethernet switches
C. The forwarding table contains the information needed to make packet-
by-packet forwarding decisions
D. The forwarding table stores only source IP addresses
Routing protocols and control-plane processes determine routes, while the
resulting forwarding information is used by the data plane to make rapid
packet-forwarding decisions.
4. Why is longest-prefix matching used in IPv4 and IPv6 routing?
A. It ensures that packets always travel through the physically shortest path
B. It prevents routers from learning multiple routes to the same destination
C. It selects the most specific matching network prefix when multiple
routes match a destination address
D. It guarantees that every packet follows the same route
Longest-prefix matching favors the route with the greatest number of
matching address bits, allowing specific subnet routes to override broader
aggregate routes.
5. Consider a router with the following forwarding entries: 10.0.0.0/8,
10.1.0.0/16, and 10.1.2.0/24. If a packet is destined for 10.1.2.45,
which entry should be selected?
,A. 10.0.0.0/8
B. 10.1.0.0/16
C. 10.1.2.0/24
D. All three entries equally
All three prefixes match the destination, but /24 is the most specific prefix.
Therefore, longest-prefix matching selects 10.1.2.0/24.
6. Which statement best characterizes the difference between distance-
vector and link-state routing algorithms?
A. Distance-vector algorithms require every router to know the entire
network topology
B. Link-state algorithms exchange only application data
C. Distance-vector algorithms exchange distance information with
neighbors, whereas link-state algorithms distribute topology information
so routers can compute paths
D. Both algorithms use exactly the same information and computation
Distance-vector routing relies on information exchanged between
neighboring routers, while link-state routing distributes link-state
information and allows each router to construct a topology database.
7. In a distance-vector routing protocol, what fundamental problem can
occur when routers receive outdated information about network
reachability?
A. Packet fragmentation
B. ARP poisoning
C. Routing loops and the count-to-infinity problem
D. TCP connection termination
Distance-vector protocols can temporarily propagate incorrect route
information, causing routers to believe that unreachable destinations
remain reachable through one another.
, 8. What is the primary purpose of the Bellman-Ford algorithm in
distance-vector routing?
A. To encrypt routing updates
B. To assign MAC addresses to interfaces
C. To compute minimum-cost paths based on distances learned from
neighboring routers
D. To translate domain names into IP addresses
Distance-vector protocols are based on the Bellman-Ford recurrence, in
which a router determines the best route by considering the cost to a
neighbor plus that neighbor's advertised distance.
9. Suppose router X can reach destination D through router Y at a cost of
4, while Y advertises a distance of 7 to D. What distance to D does X
calculate through Y?
A. 3
B. 11
C. 28
D. 74
The Bellman-Ford calculation adds the local link cost to the neighbor's
advertised distance: 4 + 7 = 11.
10. Which mechanism is commonly used by distance-vector
protocols to reduce the likelihood of routing loops in situations where
a router should not advertise a route back through the interface from
which it learned that route?
A. Flooding
B. Link-state advertisement
C. Split horizon
D. Packet fragmentation
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2027
Q&A| Instant Download Pdf.
1. In the context of computer networks, which statement most
accurately describes the primary purpose of the Internet Protocol (IP)
layer in the TCP/IP architecture?
A. To guarantee reliable, ordered delivery of application data between
processes
B. To provide end-to-end encryption for all application traffic
C. To provide logical addressing and route packets across interconnected
networks
D. To establish persistent sessions between application processes
The IP layer is responsible for logical addressing and forwarding packets
between networks. Reliability, ordering, and process-to-process
communication are primarily provided by higher-layer protocols such as
TCP.
2. A router receives an IP packet whose destination address does not
belong to any directly connected network. What does the router
normally do to determine where the packet should be forwarded?
A. It broadcasts the packet to every neighboring router
B. It sends the packet to the application layer for interpretation
,C. It consults its forwarding table and selects the best matching route
D. It changes the destination IP address to the router's own address
Routers use forwarding tables to determine the appropriate outgoing
interface and next hop. The longest-prefix-match principle is commonly
used when multiple routes match a destination address.
3. Which property distinguishes a forwarding table from a routing table
in a typical network router?
A. The forwarding table contains only application-layer information
B. The routing table is used exclusively by Ethernet switches
C. The forwarding table contains the information needed to make packet-
by-packet forwarding decisions
D. The forwarding table stores only source IP addresses
Routing protocols and control-plane processes determine routes, while the
resulting forwarding information is used by the data plane to make rapid
packet-forwarding decisions.
4. Why is longest-prefix matching used in IPv4 and IPv6 routing?
A. It ensures that packets always travel through the physically shortest path
B. It prevents routers from learning multiple routes to the same destination
C. It selects the most specific matching network prefix when multiple
routes match a destination address
D. It guarantees that every packet follows the same route
Longest-prefix matching favors the route with the greatest number of
matching address bits, allowing specific subnet routes to override broader
aggregate routes.
5. Consider a router with the following forwarding entries: 10.0.0.0/8,
10.1.0.0/16, and 10.1.2.0/24. If a packet is destined for 10.1.2.45,
which entry should be selected?
,A. 10.0.0.0/8
B. 10.1.0.0/16
C. 10.1.2.0/24
D. All three entries equally
All three prefixes match the destination, but /24 is the most specific prefix.
Therefore, longest-prefix matching selects 10.1.2.0/24.
6. Which statement best characterizes the difference between distance-
vector and link-state routing algorithms?
A. Distance-vector algorithms require every router to know the entire
network topology
B. Link-state algorithms exchange only application data
C. Distance-vector algorithms exchange distance information with
neighbors, whereas link-state algorithms distribute topology information
so routers can compute paths
D. Both algorithms use exactly the same information and computation
Distance-vector routing relies on information exchanged between
neighboring routers, while link-state routing distributes link-state
information and allows each router to construct a topology database.
7. In a distance-vector routing protocol, what fundamental problem can
occur when routers receive outdated information about network
reachability?
A. Packet fragmentation
B. ARP poisoning
C. Routing loops and the count-to-infinity problem
D. TCP connection termination
Distance-vector protocols can temporarily propagate incorrect route
information, causing routers to believe that unreachable destinations
remain reachable through one another.
, 8. What is the primary purpose of the Bellman-Ford algorithm in
distance-vector routing?
A. To encrypt routing updates
B. To assign MAC addresses to interfaces
C. To compute minimum-cost paths based on distances learned from
neighboring routers
D. To translate domain names into IP addresses
Distance-vector protocols are based on the Bellman-Ford recurrence, in
which a router determines the best route by considering the cost to a
neighbor plus that neighbor's advertised distance.
9. Suppose router X can reach destination D through router Y at a cost of
4, while Y advertises a distance of 7 to D. What distance to D does X
calculate through Y?
A. 3
B. 11
C. 28
D. 74
The Bellman-Ford calculation adds the local link cost to the neighbor's
advertised distance: 4 + 7 = 11.
10. Which mechanism is commonly used by distance-vector
protocols to reduce the likelihood of routing loops in situations where
a router should not advertise a route back through the interface from
which it learned that route?
A. Flooding
B. Link-state advertisement
C. Split horizon
D. Packet fragmentation
