Why routing determines packet paths in Computer Networks - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the sentence to explain what routing does in a network.

Computer Networks

Routing is the process of selecting [1] for data packets to travel from source to destination.

Drag options to blanks, or click blank then click option'

Apaths

Baddresses

Cprotocols

Ddevices

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing routing with addressing or devices.

Thinking routing selects protocols instead of paths.

Routing selects the paths that data packets take through a network to reach their destination.

2fill in blank

medium

Complete the sentence to describe what routers use to decide packet paths.

Computer Networks

Routers use [1] tables to determine the best path for packets.

Drag options to blanks, or click blank then click option'

Arouting

Baddress

Cprotocol

Dconnection

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'address' instead of 'routing' for the table name.

Confusing protocol tables with routing tables.

Routers use routing tables that list paths to different network destinations.

3fill in blank

hard

Fix the error in the sentence about routing decisions.

Computer Networks

Routing decides the [1] of packets based on their destination IP address.

Drag options to blanks, or click blank then click option'

Asource

Bsize

Cspeed

Dpath

Attempts:

3 left

💡 Hint

Common Mistakes

Selecting 'source' instead of 'path'.

Thinking routing controls packet size or speed.

Routing decides the path packets take, not their source, size, or speed.

4fill in blank

hard

Fill both blanks to complete the explanation of routing.

Computer Networks

Routing uses [1] to find the best [2] for packets to reach their destination efficiently.

Drag options to blanks, or click blank then click option'

Aalgorithms

Baddresses

Cpath

Ddevices

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'addresses' instead of 'algorithms' for the first blank.

Confusing 'devices' with 'path' for the second blank.

Routing uses algorithms to find the best path for packets.

5fill in blank

hard

Fill all three blanks to explain how routing affects packet delivery.

Computer Networks

When a packet arrives, the router checks the [1] address, consults the [2], and forwards the packet through the [3] interface.

Drag options to blanks, or click blank then click option'

Adestination

Brouting table

Ccorrect

Dsource

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing source and destination addresses.

Not understanding the role of the routing table.

Choosing 'wrong' instead of 'correct' for the interface.

The router checks the destination address, looks up the routing table, and sends the packet through the correct interface.

Practice

1. Why does routing determine the path that data packets take in a network?

easy

A. Because packets always follow the shortest physical cable

B. Because routers use routing tables to choose the best path

C. Because the sender decides the exact path for each packet

D. Because packets randomly select a path at each router

Solution

1. Step 1: Understand the role of routers

   Routers use routing tables to decide where to send packets next based on destination addresses.

2. Step 2: Recognize routing tables guide packet paths

   Routing tables contain information about network paths and help routers pick the best route for efficient delivery.

3. Final Answer:

   Because routers use routing tables to choose the best path -> Option B

4. Quick Check:

   Routing tables guide paths = Because routers use routing tables to choose the best path [OK]

Hint: Remember: routers use tables, not random or fixed paths [OK]

Common Mistakes:

• Thinking packets always take the shortest cable
• Believing the sender controls the entire path
• Assuming packets choose paths randomly

2. Which of the following is the correct way a router decides the next hop for a packet?

easy

A. Ignoring the destination address

B. Sending the packet back to the sender

C. Broadcasting the packet to all connected devices

D. Using a routing table to find the best next hop

Solution

1. Step 1: Identify router decision process

   Routers consult their routing tables to decide the next hop for each packet.

2. Step 2: Eliminate incorrect behaviors

   Sending back, broadcasting, or ignoring destination do not help route packets correctly.

3. Final Answer:

   Using a routing table to find the best next hop -> Option D

4. Quick Check:

   Routing table lookup = Using a routing table to find the best next hop [OK]

Hint: Routers always check routing tables first [OK]

Common Mistakes:

• Confusing routing with broadcasting
• Thinking routers ignore destination addresses
• Assuming packets are sent back to sender

3. Consider a network where Router A has the following routing table entries:
Destination: 192.168.1.0/24, Next Hop: Router B
Destination: 10.0.0.0/8, Next Hop: Router C
If a packet with destination IP 10.5.6.7 arrives at Router A, where will it be sent?

medium

A. Router B

B. Router A will drop the packet

C. Router C

D. Router A will broadcast the packet

Solution

1. Step 1: Match destination IP with routing table

   The IP 10.5.6.7 fits in the 10.0.0.0/8 range, so Router A uses the entry with next hop Router C.

2. Step 2: Determine packet forwarding

   Router A forwards the packet to Router C based on the matched routing table entry.

3. Final Answer:

   Router C -> Option C

4. Quick Check:

   IP matches 10.0.0.0/8 route = Router C [OK]

Hint: Match IP to routing table prefix to find next hop [OK]

Common Mistakes:

• Choosing Router B which matches a different subnet
• Assuming packet is dropped without match
• Thinking packet is broadcasted

4. A router's routing table is missing an entry for a destination network. What will happen to packets destined for that network?

medium

A. The router will forward packets to a default route if set

B. The router will send packets back to the sender

C. The router will broadcast packets to all networks

D. The router will ignore the packets and do nothing

Solution

1. Step 1: Understand routing table behavior

   If no specific route exists, routers check for a default route to forward packets.

2. Step 2: Identify correct fallback action

   If a default route exists, packets are sent there; otherwise, packets are dropped or an error is sent.

3. Final Answer:

   The router will forward packets to a default route if set -> Option A

4. Quick Check:

   Default route used when no match = The router will forward packets to a default route if set [OK]

Hint: Look for default route when no exact match found [OK]

Common Mistakes:

• Thinking packets are sent back to sender
• Assuming packets are broadcasted
• Believing router ignores packets silently

5. In a complex network, two routers have different routing tables for the same destination. Router X sends packets to Router Y, but Router Y sends packets back to Router X for the same destination, causing a loop. What routing concept can prevent this problem?

hard

A. Routing protocols that detect and avoid loops

B. Using static routes without updates

C. Broadcasting packets to all routers

D. Ignoring routing tables and sending packets randomly

Solution

1. Step 1: Identify the problem as a routing loop

   Packets keep moving between routers without reaching destination, indicating a loop.

2. Step 2: Understand routing protocol role

   Routing protocols like RIP or OSPF include mechanisms to detect loops and prevent them by updating routes.

3. Step 3: Recognize correct solution

   Using routing protocols that detect and avoid loops stops packets from circulating endlessly.

4. Final Answer:

   Routing protocols that detect and avoid loops -> Option A

5. Quick Check:

   Loop prevention = Routing protocols [OK]

Hint: Use routing protocols to stop loops in paths [OK]

Common Mistakes:

• Thinking static routes fix loops automatically
• Believing broadcasting solves routing loops
• Ignoring routing tables causes more problems