Computer Networks Questions & Answers – OSPF
1. Open Shortest Path First (OSPF)
is also called as _____________
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) All of the mentioned
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) All of the mentioned
Answer: a
Explanation: Each OSPF router monitors the cost of the link to each of its neighbours and then floods the link state information to other routers in the network.
Explanation: Each OSPF router monitors the cost of the link to each of its neighbours and then floods the link state information to other routers in the network.
2. The computation of the shortest
path in OSPF is usually done by ____________
a) Bellman-ford algorithm
b) Routing information protocol
c) Dijkstra’s algorithm
d) Distance vector routing
a) Bellman-ford algorithm
b) Routing information protocol
c) Dijkstra’s algorithm
d) Distance vector routing
Answer: c
Explanation: Shortest path in OSPF is usually computed by Dijkstra’s algorithm. It was proposed by Edsger W. Dijkstra in the year 1956. This algorithm computes the shortest path between nodes.
Explanation: Shortest path in OSPF is usually computed by Dijkstra’s algorithm. It was proposed by Edsger W. Dijkstra in the year 1956. This algorithm computes the shortest path between nodes.
3. Which of the following is false
with respect to the features of OSPF?
a) Support for fixed-length sunbathing by including the subnet mask in the routing message
b) More flexible link cost than can range from 1 to 65535
c) Use of designated router
d) Distribution of traffic over multiple paths that have equal cost to the destination
a) Support for fixed-length sunbathing by including the subnet mask in the routing message
b) More flexible link cost than can range from 1 to 65535
c) Use of designated router
d) Distribution of traffic over multiple paths that have equal cost to the destination
Answer: a
Explanation: Support for variable-length sunbathing by including the subnet mask in the routing message.
Explanation: Support for variable-length sunbathing by including the subnet mask in the routing message.
4. In OSPF, which protocol is used
to discover neighbour routers automatically?
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) Hello protocol
a) Link state protocol
b) Error-correction protocol
c) Routing information protocol
d) Hello protocol
Answer: d
Explanation: Hello protocol is used to discover neighbour routers automatically. It makes sure that the communication between neighbors are bidirectional.
Explanation: Hello protocol is used to discover neighbour routers automatically. It makes sure that the communication between neighbors are bidirectional.
5. Which of the following is not a
type of OSPF packet?
a) Hello
b) Link-state request
c) Link-state response
d) Link-state ACK
a) Hello
b) Link-state request
c) Link-state response
d) Link-state ACK
Answer: c
Explanation: Five types of OSPF packets are: Hello, Database description, Link-state request, Link-state update, Link-state ACK.
Explanation: Five types of OSPF packets are: Hello, Database description, Link-state request, Link-state update, Link-state ACK.
6. Correct order of the operations
of OSPF.
1 – Hello packets
2 – Propagation of link-state information and building of routing tables
3 – Establishing adjacencies and synchronisation database
a) 1-2-3
b) 1-3-2
c) 3-2-1
d) 2-1-3
1 – Hello packets
2 – Propagation of link-state information and building of routing tables
3 – Establishing adjacencies and synchronisation database
a) 1-2-3
b) 1-3-2
c) 3-2-1
d) 2-1-3
Answer: b
Explanation: OSPF first implements a hello protocol. Then it later on tries to establish synchronisation with database. Later on building of routing tables is done.
Explanation: OSPF first implements a hello protocol. Then it later on tries to establish synchronisation with database. Later on building of routing tables is done.
7. In OSPF header, which field is
used to detect errors in the packet?
a) Type
b) Area ID
c) Authentication type
d) Checksum
a) Type
b) Area ID
c) Authentication type
d) Checksum
Answer: d
Explanation: Checksum field is used to detect errors. It makes sure that the data portions that are being sent are all in integrity. It can detect duplicated bits.
Explanation: Checksum field is used to detect errors. It makes sure that the data portions that are being sent are all in integrity. It can detect duplicated bits.
8. In OSPF database descriptor
packet, if more database descriptor packet flows, ‘M’ field is set to
____________
a) 1
b) 0
c) more
d) none
a) 1
b) 0
c) more
d) none
Answer: a
Explanation: M bit is set to 1.
Explanation: M bit is set to 1.
9. In OSPF database descriptor
packet, which field is used to indicate that the router is master?
a) M
b) MS
c) I
d) Options
a) M
b) MS
c) I
d) Options
Answer: b
Explanation: M bit is set to 1. These packets are exchanged when an adjacency is being initialized. Master sends these packets called polls to slave, and then slave sends back acknowledgments.
Explanation: M bit is set to 1. These packets are exchanged when an adjacency is being initialized. Master sends these packets called polls to slave, and then slave sends back acknowledgments.
10. In OSPF database descriptor
packet, which field is used to detect a missing packet?
a) LSA header
b) MS
c) Database descriptor sequence number
d) Options
a) LSA header
b) MS
c) Database descriptor sequence number
d) Options
Answer: c
Explanation: Sequence number field is used to detect a missing packet. LSA is abbreviation for link state advertisement. LSA is the main communication means for OSPF.
Explanation: Sequence number field is used to detect a missing packet. LSA is abbreviation for link state advertisement. LSA is the main communication means for OSPF.
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