This set of Computer Networks Multiple Choice Questions & Answers (MCQs) focuses on “LS Routing Algorithms”.
1. Which routing algorithm was replaced by link state routing algorithm in the ARPANET?
a) Path routing
b) Distance vector routing
c) Broadcast routing
d) Multicast routing
View Answer
Explanation: Originally, the ARPANET used distance vector routing in it but later it was replaced by link state routing. This is because of the count-to-infinity problem in distance vector routing. Unlike DVR, routing tables in LS routing contain whole topology of the network.
2. Same topology is used by all the nodes to construct a routing table in link state routing.
a) True
b) False
View Answer
Explanation: In link state routing, the routing tables are different but the topology they perceive is same. Because of this same topology, each node will have a shortest path for every node in the network.
3. What is flooding in link state routing in case of exchanging topology information?
a) Exposing routing tables to neighbors
b) Sending duplicate packets to nodes
c) Communicating with every router using messages
d) Spreading link state packets
View Answer
Explanation: Link state packets are used to spread the information about the topology from one node to all nodes. It can be periodic or triggered and it carries information about both topology and itself to other nodes.
4. Which information in the link state packets helps in discarding old link state packets?
a) Information about topology
b) Sequence number
c) Age
d) Number of nodes it visits
View Answer
Explanation: Every link state packet, which is created by a node will have the data about its age. This age information is used to dispose the old packets from the domain which are timed out.
5. Which sequence of procedure is correct to build a routing table in link state routing?
a) Creating LSP – flooding – shortest path tree – calculating routing table
b) Shortest path tree – flooding – creating LSP – calculating routing table
c) Creating LSP – flooding – calculating routing table – shortest path tree
d) Shortest path tree – flooding – calculating routing table -creating LSP
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Explanation: Once all nodes get familiar with the topology using flooding, which is done using LSP, then a shortest path tree will be constructed for each node. Shortest path trees are used to calculate the routing tables and each router will have one shortest path tree.
6. Which algorithm is used by the router in the link state routing to find the shortest paths?
a) OSPF
b) RIP
c) Dijkstra algorithm
d) BGP
View Answer
Explanation: Shortest path trees will be constructed to build the routing tables and router uses Dijkstra algorithm to compute the routes. Dijkstra algorithm finds the shortest route for every destination in the network for a router and this information will be memorized.
7. Which algorithm is implemented based on link state routing?
a) OSPF
b) BGP
c) RIP
d) OSLR
View Answer
Explanation: Open shortest path first(OSPF) is based on link state routing which works in an autonomous domain and it is a dynamic routing protocol. This protocol works well by dividing the autonomous system into areas.
8. Which of the following is an advantage of the link state routing?
a) Uses more memory
b) Flood of advertisements
c) Less routing loops
d) Need for administrator
View Answer
Explanation: Link state routing causes less loops when compared to distance vector routing. It is because, complete topology information will be there at each router and this information prevents misunderstandings which leads to loops.
9. What is the full form of LSA in link state routing, which is used to exchange information between routers?
a) Line state autonomy
b) Line state advertisement
c) Link state advertisement
d) Link sate for autonomous
View Answer
Explanation: Routers share the information about topology using link state advertisements. There will be a continuous process of passing these link state advertisements until every router get the full topology of the network.
10. Link state routing is confined to inter-domain routing.
a) True
b) False
View Answer
Explanation: Link state routing can be used within the autonomous system only, because flooding is unmanageable in a large network. Because, network is a collection of such autonomous systems.
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