Question 1easymultiple choice
Full question →easymultiple choiceObjective-mapped
At which OSI layer do routers make forwarding decisions based on logical addressing?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Layer 1
Layer 1 is the physical layer.
B
Distractor review
Layer 2
Layer 2 switching uses MAC addresses, not routed logical forwarding decisions.
C
Best answer
Layer 3
Correct. Layer 3 is the network layer.
D
Distractor review
Layer 4
Layer 4 involves transport concepts such as TCP and UDP.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting Layer 2 or Layer 4 as the layer where routers make forwarding decisions. Many candidates mistakenly associate forwarding with MAC addresses at Layer 2 or confuse routing with transport layer functions at Layer 4, such as TCP/UDP port handling. However, routers do not use MAC addresses to route packets between networks; they rely on logical IP addresses at Layer 3. Misunderstanding this leads to incorrect answers, especially when questions focus on routing versus switching or transport concepts. Remember, routing decisions are strictly a Layer 3 function involving IP addressing and routing protocols.
Technical deep dive
How to think about this question
The OSI model divides network communication into seven layers, each with distinct functions. Layer 3, the Network layer, is responsible for logical addressing and routing packets between different networks. Routers operate at this layer, using logical addresses such as IPv4 or IPv6 to determine the best path for forwarding packets. Unlike Layer 2 switches that use MAC addresses, routers analyze Layer 3 addresses to make forwarding decisions across diverse network segments. Routers examine the destination IP address in the packet header and consult their routing table to decide the next hop. This decision process involves comparing network prefixes, applying routing protocols like OSPF or EIGRP to learn routes, and selecting the optimal path based on metrics and administrative distance. The router then forwards the packet out the appropriate interface toward its destination network, enabling internetwork communication. A common exam trap is confusing Layer 3 routing with Layer 2 switching or Layer 1 physical transmission. While switches forward frames based on MAC addresses at Layer 2, routers forward packets based on logical Layer 3 addresses. Practically, this means routers enable communication between different IP subnets, which switches alone cannot do. Understanding this distinction is critical for CCNA routing topics and for configuring networks that require inter-VLAN routing or WAN connectivity.
KKey Concepts to Remember
- Routers use logical Layer 3 addresses such as IPv4 or IPv6 to make forwarding decisions between different networks.
- Routing involves consulting a routing table to select the best path based on metrics and administrative distance.
- Layer 2 switches forward frames based on MAC addresses and cannot route packets between different IP subnets.
- Routing protocols like OSPF and EIGRP help routers learn and advertise routes to build their routing tables.
- Layer 1 deals with physical transmission and does not involve forwarding decisions based on addressing.
- Layer 4 manages transport layer functions such as TCP and UDP but does not perform packet forwarding between networks.
- Routers enable internetwork communication by forwarding packets based on logical addressing at Layer 3.
- Confusing Layer 2 switching with Layer 3 routing is a common exam mistake that leads to incorrect answers.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
Routers use logical Layer 3 addresses such as IPv4 or IPv6 to make forwarding decisions between different networks.
What is the correct answer to this question?
The correct answer is: Layer 3 — Routers operate at the network layer when making forwarding decisions based on logical Layer 3 addresses such as IPv4 or IPv6 destination addresses.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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