20 Routing Protocols Interview Questions and Answers

Routing protocols are the set of rules that govern how data is exchanged between network devices. When applying for a network administrator or engineer position, it is likely that you will be asked questions about routing protocols during the interview process. Answering these questions correctly can help you demonstrate your knowledge and secure the job. In this article, we will review some common routing protocols interview questions and provide tips on how to answer them.

Routing Protocols Interview Questions and Answers

Here are 20 commonly asked Routing Protocols interview questions and answers to prepare you for your interview:

1. Can you explain what routing is?

Routing is the process of finding a path between two or more network nodes. A routing protocol is a set of rules that govern how routers communicate with each other to exchange information about the best routes between nodes.

2. What are the different types of routing protocols?

There are three main types of routing protocols: link-state, distance-vector, and hybrid. Link-state routing protocols keep track of the topology of the network and use that information to make routing decisions. Distance-vector routing protocols make decisions based on the distance to the destination, while hybrid routing protocols use a combination of both methods.

3. Why do we need multiple routing protocols in a data center environment?

In a data center environment, we need multiple routing protocols to provide redundancy and to ensure that data can still flow even if one of the routing protocols fails. By having multiple routing protocols, we can also provide different levels of service to different types of traffic.

4. What are some common problems with RIP and OSPF?

Some common problems with RIP include the fact that it does not scale well to large networks and that it does not support variable-length subnet masks. OSPF, on the other hand, can have problems with slow convergence and high resource consumption.

5. How does BGP work?

BGP (Border Gateway Protocol) is a routing protocol used to exchange routing and reachability information between autonomous systems (AS) on the Internet. BGP uses a path vector algorithm to decide which route is the best path to a certain destination. BGP is the protocol used to make the core of the Internet work.

6. Can you explain how distance-vector routing protocols like RIP, IGRP and EIGRP work?

Distance-vector routing protocols work by each router sending its entire routing table to every other router in the network periodically. This means that every router has the same information about the network and can make routing decisions based on that information. The main disadvantage of this type of routing protocol is that it can be slow to converge on a new network topology.

7. What’s your opinion about dynamic vs static routing for networks spanning several locations?

There are pros and cons to both dynamic and static routing. With dynamic routing, you have the benefit of the routing protocol automatically updating the routing table as changes occur in the network. This can be a big time saver, especially in larger networks. However, dynamic routing can also be less reliable, as it is reliant on the routing protocol working correctly. Static routing, on the other hand, is more reliable, as the routing table is manually configured. However, this means that any changes to the network must be manually updated in the routing table, which can be time-consuming. In the end, it really depends on the specific needs of the network as to which type of routing is best.

8. What is the difference between link state and distance vector routing protocols? Which one would you prefer in certain situations?

Link state routing protocols are more accurate but require more processing power than distance vector routing protocols. I would prefer to use a link state routing protocol in situations where accuracy is more important than speed.

9. Can you compare and contrast BGP versions 4 and 6?

BGP4 is the original version of the Border Gateway Protocol, while BGP6 is the most recent version. BGP4 is more commonly used than BGP6, but BGP6 offers a number of advantages, including support for IPv6 addresses and a simpler configuration.

10. What happens if there are two or more paths to the same network with different metrics? Which path will be chosen?

In the event that there are two or more paths to the same network with different metrics, the path with the lowest metric will be chosen.

11. What’s the difference between an autonomous system and a domain?

An autonomous system (AS) is a collection of IP networks and routers under the control of a single administrative entity. A domain is a logical grouping of ASes that share a common routing policy.

12. How often is route information advertised by routers using RIP, OSPF, and BGP?

RIP and OSPF routers send out updates every 30 seconds, while BGP routers only send updates when there is a change in the network.

13. What is a default route? Is it good practice to use a default route on all routers?

A default route is a route that is used when no other route is available. It is typically used as a catch-all for when a specific route cannot be determined. While it is not necessarily bad practice to use a default route on all routers, it is generally considered best practice to only use it as a last resort.

14. What is the purpose of the metric value associated with each route entry?

The metric value is used by the routing protocol to determine the best path to a destination. The metric value is usually a combination of the cost of the link and the distance to the destination.

15. What do you understand by asymmetric routing?

Asymmetric routing is a routing configuration in which traffic from a given source to a given destination can take two different paths. This can happen for a variety of reasons, but often has to do with one path being faster or more direct than the other.

16. What is the Border Gateway Protocol (BGP) used for?

The Border Gateway Protocol (BGP) is a routing protocol used to exchange routing and reachability information between autonomous systems (AS) on the Internet. BGP is the only exterior gateway protocol (EGP) in use today.

17. What happens when you advertise routes via BGP and then remove them?

When you advertise routes via BGP and then remove them, the routes are no longer advertised but they are not removed from the BGP routing table. This can cause problems because other BGP routers may still have the route in their routing table and continue to try and send traffic that way, even though the route is no longer active.

18. How do you configure iBGP sessions? What ports do they run on? What encryption methods can be used?

iBGP sessions are configured using the router bgp command, and they run on port 179. iBGP sessions can be encrypted using various methods, such as Transport Layer Security (TLS) or Internet Protocol Security (IPSec).

19. What is a next hop router?

A next hop router is a router that is used to forward packets to the next hop in the network. In order to do this, the router must have a route to the next hop router. The next hop router is typically the next router in the network that the packet needs to be forwarded to in order to reach its destination.

20. What is classless interdomain routing?

Classless interdomain routing (CIDR) is a method for allocating IP addresses and routing IP packets. CIDR is an alternative to the traditional classful network architecture. In a classful network, addresses are divided into classes (A, B, and C), with each class having a different number of bits assigned to the network portion of the address. In a classless network, the number of bits assigned to the network portion of the address can be any value, allowing for a more efficient use of IP addresses.