---
title: "Routing and need of routing protocol"
subject: "Computer Networks and Security"
chapter: 4
key: "semester_7/computer_networks_and_security:routing-protocol-necessity"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/routing-protocol-necessity
site: BCT Engineering
---

# Routing and need of routing protocol

Computer Networks and Security · Chapter 4: Network Layer

- Asked in: 2071 Shrawan, 2 marks; 2069 Chaitra, 3 marks (asked 2 times)
- Video: [What are Routing Protocols and their Types?](https://www.youtube.com/watch?v=pAopv0-lKxY) — NETWORK WALKS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/routing-protocol-necessity
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-4

## Question

What is routing? Why is a routing protocol necessary?

## Short answer

Routing selects the best path for packets. Dynamic routing protocols automatically build routing tables, adapt to topology changes, select optimal paths using metrics, scale to large networks, avoid loops, and enable load balancing without manual configuration.

## Answer

#### Routing
**Routing** is the process of selecting the best path along which a packet travels from the source network to the destination network across an internetwork. It is the main function of the network layer and is done by routers using routing tables.

#### Why a routing protocol is necessary
1. **Automatic building of routing tables:** in a large network, entering routes by hand (static routing) is not practical. A routing protocol lets routers exchange information and learn routes themselves.
2. **Adapting to changes:** if a link fails or a new network is added, the protocol updates the tables (dynamic routing), giving fault tolerance.
3. **Best path selection:** it uses metrics such as hop count, bandwidth, delay and cost to select the optimal route.
4. **Scalability:** the Internet has millions of networks, which no administrator can configure by hand.
5. **Load balancing and reliability** through alternative routes.
6. **Loop avoidance** and consistent view of the network by all routers.

Examples: RIP, OSPF (interior); BGP (exterior).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is routing?
   A. Splitting frames
   B. Selecting the best path for a packet across an internetwork
   C. Assigning MACs
   D. Error checking
   Answer: B. Routing is the main network layer function. (Key point: Routing)

2. Why can't static routing scale?
   A. Manual entry is impractical in large networks and cannot adapt to failures
   B. It is too fast
   C. It uses UDP
   D. It has no tables
   Answer: A. Routing protocols build tables automatically and adapt. (Key point: Dynamic need)

3. What does a routing protocol use to pick the optimal route?
   A. MAC address
   B. Metrics such as hop count, bandwidth, delay and cost
   C. Port number
   D. Frame size
   Answer: B. Metrics enable best path selection. (Key point: Metrics)

## Related in Computer Networks and Security

- [Routing Information Protocol (RIP)](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Arip-protocol) — Computer Networks and Security, chapter 4
- [Routed vs routing protocol](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Arouted-vs-routing-protocol) — Computer Networks and Security, chapter 4

## Related in other subjects

- [Communication protocol and its need](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Acommunication-protocol-need) — Telecommunications, chapter 8, asked 3×
- [Link-state routing as adaptive routing](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Alink-state-adaptive-example) — Telecommunications, chapter 8
- [Routing factors and avoiding crosstalk](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Aroute-factors-crosstalk) — Instrumentation II, chapter 8