Router and Routing Algorithm MCQ Quiz - Objective Question with Answer for Router and Routing Algorithm - Download Free PDF

EXPLANATION:

When an IP datagram is transmitted from Host A to Host B, some fields in the IP header may change, while others remain the same. Here's the breakdown of each field mentioned:

• (A) TTL (Time-to-Live):
  • The TTL field is decremented by each router the datagram passes through. This ensures that packets don't loop indefinitely in the network. Therefore, the TTL will differ when the packet reaches Host B.
• (B) Checksum:
  • The IP header checksum will change as the packet travels through the network, especially when the TTL field is decremented. Since TTL changes, the checksum needs to be recalculated by each router to account for this change. Hence, the checksum will be different.
• (C) Fragment Offset:
  • If the datagram was fragmented during transmission, the Fragment Offset field may change. This field is used to indicate where a particular fragment belongs in the original datagram. If no fragmentation occurred, this field remains unchanged, but if fragmentation occurs, it will differ.
• (D) Source IP:
  • The Source IP address remains unchanged throughout the journey of the datagram because it identifies the sender of the packet. It will not change during transmission.
• (E) Destination IP:
  • Similarly, the Destination IP address also remains unchanged because it specifies the intended recipient of the packet. It will not change during transmission.

Thus, the correct answer is Option 2: (A), (B), and (C) Only. 

The correct answer is Finding the best path for data

Key Points

• In the context of networking, the network layer is responsible for routing data packets from the source to the destination across an internetwork, which may consist of multiple interconnected networks.
• The primary function of routing within the network layer is to determine the best path for data packets to reach their intended destination.
• When data is transmitted over a network, it is divided into smaller units called packets.
• These packets contain both the actual data being transmitted and control information, including source and destination addresses.
• The routing process involves making decisions about how to forward these packets through the network based on the destination address.

Hub and switch is the central device in a star topology.

Star networks are one of the most common computer network topologies.

In its simplest form, a star network consists of one central node, typically a switch or hub, which acts as a conduit to transmit messages. In star topology, every node is connected to a central node.

The switch is the server and the peripherals are the clients.

The correct answer is Determining the best path for data packets

Key Points

• Determining the best path for data packets:
  • ​This is the core function of routing. When data is transmitted across a network, routers analyze the destination address of the packets and make decisions on the most efficient path to reach that destination.
  • This involves considering factors like the current network conditions, available paths, and routing protocols.

The correct answer is Finding the best path for data

Key Points

• In the context of networking, the network layer is responsible for routing data packets from the source to the destination across an internetwork, which may consist of multiple interconnected networks.
• The primary function of routing within the network layer is to determine the best path for data packets to reach their intended destination.
• When data is transmitted over a network, it is divided into smaller units called packets.
• These packets contain both the actual data being transmitted and control information, including source and destination addresses.
• The routing process involves making decisions about how to forward these packets through the network based on the destination address.

The correct option is (3)

Determines on which outing link a packet is to be forwarded

Concept:-

Among computer networks, a router is a networking device that forwards data packets. Packet switching, packet filtering, network communication, and path selection are all services offered by routers.

Key Points

• On computer networks, a router receives and transmits data. Occasionally, network hubs, modems, and network switches are mistaken for routers.
• To increase internet access or assist in the creation of business networks, routers can integrate the operations of various parts and interact with these gadgets.
• Using routing tables and subnet information, each router forwards packets to the router after it.
• The packet is routed until it reaches the target network. The last router uses the local ID connected to the destination GID to forward packets to their destination.
• Each router examines and sends each IP packet individually - this is called packet switching.
• The router passes the packet to another router that is listed in its routing table if the table does not have the destination address.

The correct answer is Gateway.

Key Points

• A gateway serves as the entry and exit point of a network. It acts as a communication point or interface between different networks, allowing data to pass through it in order to use routing paths.
• Gateways are responsible for protocol translation, security enforcement, and network traffic management.
• They can connect networks that use different protocols, such as connecting a local area network (LAN) to the internet.

Additional Information 

• Network Interface: A gateway is equipped with multiple network interfaces to connect different networks. It can have connections to the internet, local area networks (LANs), wide area networks (WANs), or other networks.
• Protocol Translation: Gateways are responsible for translating protocols between different networks. They can convert data packets from one protocol to another, allowing communication between networks that use different standards or languages.
• Traffic Routing: When data enters a network, it must pass through the gateway. The gateway examines the packet's destination address and determines the best routing path for the data to reach its intended destination. It helps direct traffic efficiently within the network or between different networks.
• Network Address Translation (NAT): Gateways often perform Network Address Translation, which allows multiple devices on a LAN to share a single public IP address. It masks the private IP addresses of devices behind the gateway's public IP address, enhancing security and conserving IP addresses.

An amplifier cannot discriminate between the intended signal and noise; it amplifies equally everything fed into it. A repeater dots not amplify the signal; it regenerates the signal. When it receives a weakened or corrupted signal, it creates a copy, bit for bit, at the original strength.

A router will not change the source address of the packet, rest of the given fields can be changed at the router.

Checksum: Checksum field changes at every router in correspondence with the change in values of other fields.

TTL (Time to Live): After every hop, the TTL field is reduced by one. Hence this field changes at every router.

Length: If fragment - apian is required length field will certainly change.

Gateway : A gateway is normally a computer that operates in all layers of OSI model. It takes an application message, reads it and interprets it. It can be used as a connecting device between two internetworks that use different models. It understands the format and contents of data and translate message from one format to another.

Hub: Hub is a physical layer device used to connect multiple devices in the network. It has many ports. It uses half duplex transmission mode. If a device wants to connect to the network then it can be connected to one of these ports.

Router : Router is a network layer device. It transform the message in the form of packets. It uses routing tables to transfer the data across the network.

Switches : Switch is a data link layer device used to connect devices. It uses packet switching technology to send and receive the data across the network. Full duplex transmission mode is used in switching.

The correct answer is "option 4".

CONCEPT:

The routing algorithm is a procedure that determines the best route to send the packets from source to destination.

The routing algorithm chooses among different paths, when data packets leave their source, to reach the destination.

Option 1: Incorrect

In the Distance Vector algorithm, routers advertise the path & distance(metric) for each reachable destination within the network to adjacent hosts.

This routing algorithm is used by Routing Information Protocol(RIP).

Option 2: Incorrect

Flooding is a routing technique in which the source sends the packet through every outgoing link.

In Flooding, every incoming packet is sent through outgoing links except where it has arrived.

Option 3: Incorrect

Path vector algorithm is a network routing protocol that maintains the path information that gets direct dynamically.

This routing algorithm used by Border Gateway Protocol(BGP).

Option 4: correct

Link-state protocols such as IS-IS and OSPF rely on each router to advertise the state of each link to every router within the local network.

Hence, the correct answer is "option 4".

Additional Information

1.Metric is the factor that is used to determine the best path to a destination network.

2.RIP uses Hop count as its metric.

3.OSPF uses Cost as its metric.

RIP and BGP are two popular examples of distance vector routing protocols.

Important Points

Routing Information Protocol (RIP)

It is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from source to destination. The largest number of hops allowed for RIP is 15, which limits the size of networks that RIP can support.

Border Gateway Protocol (BGP)

It is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet. BGP is classified as a path-vector routing protocol, and it makes routing decisions based on paths, network policies, or rule-sets configured by a network administrator.

Additional Information

OSPF (Open Shortest Path First)

This protocol is one of a family of IP Routing protocols, and is an Interior Gateway Protocol (IGP) for the Internet, used to distribute IP routing information throughout a single Autonomous System (AS) in an IP network.

SPF

It establishes a method for receiving mail servers to verify that incoming email from a domain was sent from a host authorized by that domain’s administrators. It piggybacks on the well-established Domain Name System (DNS). 

Concept:

• Each time when packet visits network layer it decrement it’s TTL value
• TTL value decrement at router (goes to network layer to make a routing decision) and receiver end (check whether it is 0 or not) only.
• Inside LAN it never goes to Network layer so TTL will not be decremented.

Explanation:

We can see in above diagram total 5 router and one receiver end, so total 6 will be decremented from 32.

Final TTL = 32 - 6 = 26

Hence 26 is the correct answer.

The correct answer is router

Key Points 

• A "router" is a device that forwards packets between networks by processing the routing information included in the packet. 
• A router's primary function is to direct or 'route' traffic on a network.
• It does this by using headers and forwarding tables to determine the most efficient path for forwarding the packets it receives.
• Routers connect multiple networks together, and these networks could be in the same location or across wide distances (like in the case of the internet).
• They could be in residential home networks connecting personal devices to the internet, or in huge corporate networks connecting various departments and branches.
• Routers can understand and analyze the contents of the packets passing through them.
• This allows them to manage network traffic and perform tasks like IP address assignment (using DHCP) or network security functions from firewall rules or VPN configurations.

The correct answer is option 2.

Distance-vector protocols :

Distance-vector protocols update the routing tables of routers and determine the route on which a packet will be sent by the next hop which is the exit interface of the router and the IP address of the interface of the receiving router. Distance is a measure of the cost to reach a certain node.

A distance-vector routing (DVR) protocol requires that a router inform its neighbors of topology changes periodically. Historically known as the old ARPANET routing algorithm (or known as the Bellman-Ford algorithm).

Bellman-Ford Basics – Each router maintains a Distance Vector table containing the distance between itself and ALL possible destination nodes. Distances, based on a chosen metric, are computed using information from the neighbors’ distance vectors.

The given diagram is, 

 if link V1-V4 is removed then routing table.

Hence the correct answer is (0, 3, 8, 5, 11).