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Computer Networks · Question Set
Routing Algorithms & Protocols interview questions for placements and exams.
Questions
13
Included in this set
Subject
Computer Networks
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Computer Networks.
Convergence refers to the state when all routers in a network have consistent and updated routing tables. After a topology change, routing protocols exchange updates until they agree on the new paths. Fast convergence is essential for reliability, preventing loops and packet loss. OSPF and EIGRP converge faster than distance-vector protocols like RIP.
For complete preparation, combine this set with full subject-wise practice for Computer Networks. You can also explore other subjects and sets from the links below.
Routing is the process of selecting paths in a network along which data packets travel from a source to a destination. Routers use routing tables and algorithms to decide the optimal path based on metrics like distance, cost, or congestion.
In Distance Vector Routing, each router maintains a table listing the shortest distance to every other node and the direction (next hop) to reach it. Routers exchange their tables periodically with neighbors and update routes using the Bellman-Ford algorithm. The simplicity makes it easy to implement but it suffers from slow convergence and routing loops. Protocols like RIP use this approach.
The Routing Information Protocol (RIP) uses hop count to determine the shortest path. The maximum allowed hops are 15, meaning larger networks are unsuitable for RIP. Despite its limitations, RIP is widely used in small and academic networks.
Open Shortest Path First (OSPF) is a link-state protocol that uses Dijkstra’s algorithm to compute the shortest path tree. It divides a large network into areas to improve scalability. Unlike RIP, which exchanges periodic updates, OSPF sends updates only when changes occur, reducing overhead. OSPF supports authentication, hierarchical design, and faster convergence, making it suitable for enterprise networks.
A routing table lists destination IP networks, their next-hop addresses, and the cost or metric to reach them. Routers refer to these tables to forward packets efficiently toward their destination.
The default route serves as a catch-all path for packets that don’t match any specific route in the table. It’s typically used to send traffic toward the Internet through a default gateway.
Routing loops occur when packets circulate endlessly between routers due to incorrect routing information. They waste bandwidth and degrade network performance. Solutions include Split Horizon (preventing routers from advertising routes back on the same interface), Route Poisoning, and Hold-Down timers. Modern link-state protocols avoid loops through consistent network maps and sequence numbers.
Administrative Distance (AD) defines the trustworthiness of a route learned from a particular protocol. Lower AD values indicate more preferred routes. For example, OSPF has AD 110 while RIP has AD 120, so routers prefer OSPF routes when both exist.
Routing metrics quantify route desirability using parameters like hop count, delay, bandwidth, or load. MAC address length is not relevant for routing decisions since it belongs to the Data Link Layer.
Hierarchical routing divides a large network into regions or areas, allowing routers to maintain smaller routing tables. Each region summarizes routes before advertising them externally, reducing overhead and improving scalability. OSPF uses this concept by creating backbone and area routers. This design keeps large networks stable and efficient.
In Link State Routing, routers discover their neighbors, measure link costs, and flood this information to all other routers. Each router builds a full map of the network and computes the shortest paths using Dijkstra’s algorithm. It converges faster and is more scalable than distance vector routing.
BGP is an inter-domain routing protocol used to exchange routes between autonomous systems (AS). It helps maintain the global Internet routing table. BGP relies on path vector mechanisms and policies rather than shortest paths, focusing on scalability and policy control.