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Network Infrastructure and ConnectivityhardConfigurationObjective-mapped

CCNA Network Infrastructure and Connectivity Practice Question

This 200-301 practice question tests your understanding of network infrastructure and connectivity. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.

Network Topology
G0/0192.0.2.1/30G0/0192.0.2.2/302km fiberR1R2

You are connected to R1 via console. The link between R1 and R2 is experiencing packet loss and CRC errors. Configure interface speed and duplex on R1's GigabitEthernet0/0 to match R2's settings, then replace the SFP module with one that supports the required 2 km distance. Finally, verify the interface is operational without errors.

Question 1hardConfiguration
Full question →

Exhibit

R1# show interfaces GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
  Hardware is Gigabit Ethernet, address is aaaa.bbbb.cccc (bia aaaa.bbbb.cccc)
  Internet address is 192.0.2.1/30
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, link type is auto, media type is SFP
  output flow-control is unsupported, input flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:02, output 00:00:00, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 2000 bits/sec, 2 packets/sec
  5 minute output rate 1000 bits/sec, 1 packets/sec
     500 packets input, 45000 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicasts)
     0 runts, 0 giants, 0 throttles
     150 input errors, 150 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     400 packets output, 40000 bytes, 0 underruns
     0 output errors, 0 collisions, 2 interface resets
     0 unknown protocol drops
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 pause output
     0 output buffer failures, 0 output buffers swapped out

R1# show running-config interface GigabitEthernet0/0
Building configuration...

Current configuration : 120 bytes
!
interface GigabitEthernet0/0
 ip address 192.0.2.1 255.255.255.252
 duplex auto
 speed auto
 media-type sfp
 negotiation auto
end

R1# show interfaces transceiver
Interface    Vendor    Type    Serial            Part No.          Distance
Gi0/0        Cisco     SFP-GE-SX    ABC123    SFP-GE-SX          550m

R2 (via show): R2's Gi0/0 is configured with: speed 1000, duplex full

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

Configure speed 1000, duplex full, and no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

The CRC errors indicate a duplex mismatch or faulty medium. R1 is set to auto-negotiation while R2 is hardcoded to 1000/full, causing mismatch. First, set speed and duplex on R1 to match R2: 'speed 1000' and 'duplex full'. Also disable auto-negotiation with 'no negotiation auto'. The existing SFP-GE-SX only supports 550m, but the link requires 2 km; replace it with a 1000BASE-LX/LH SFP (SFP-GE-L) which supports up to 10 km. After changes, verify with 'show interfaces Gi0/0' to confirm no CRC errors and correct speed/duplex.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Configure speed 1000, duplex full, and no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

    Why this is correct

    This is correct because R1 must match R2's hardcoded 1000/full settings. Disabling auto-negotiation with 'no negotiation auto' ensures no mismatch. The SFP-GE-SX only supports 550m, so replacing it with SFP-GE-L (1000BASE-LX/LH) supports the required 2 km distance.

    Related concept

    Read the scenario before looking for a memorised answer.

  • Configure speed 1000 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-SX-MM.

    Why it's wrong here

    This is incorrect because while the speed and duplex settings are correct, the SFP-GE-SX-MM is a multimode SFP that still only supports up to 550m, not the required 2 km.

  • Configure speed 100 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

    Why it's wrong here

    This is incorrect because setting speed to 100 would cause a speed mismatch with R2's 1000 Mbps setting, leading to the interface not coming up or further errors.

  • Configure no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.

    Why it's wrong here

    This is incorrect because disabling auto-negotiation without explicitly setting speed and duplex leaves the interface in a default state that may not match R2's hardcoded 1000/full, causing a duplex mismatch.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Configure speed 1000, duplex full, and no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.Correct answer

Why this is correct

This is correct because R1 must match R2's hardcoded 1000/full settings. Disabling auto-negotiation with 'no negotiation auto' ensures no mismatch. The SFP-GE-SX only supports 550m, so replacing it with SFP-GE-L (1000BASE-LX/LH) supports the required 2 km distance.

Configure speed 1000 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-SX-MM.Wrong answer — click to see why

Why this is wrong here

The SFP-GE-SX-MM is a multimode SFP with the same distance limitation as the original SFP-GE-SX.

Why candidates choose this

Candidates might think 'MM' stands for 'more' or 'medium' and assume it supports longer distances, but it actually stands for multimode.

Configure speed 100 and duplex full on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.Wrong answer — click to see why

Why this is wrong here

The speed must match exactly; 100 Mbps is not compatible with 1000 Mbps.

Why candidates choose this

Candidates might confuse speed settings or think that 100/full is a common setting for older links.

Configure no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L.Wrong answer — click to see why

Why this is wrong here

When auto-negotiation is disabled, speed and duplex must be manually set; otherwise, the interface may default to half-duplex or other incompatible settings.

Why candidates choose this

Candidates might think that disabling auto-negotiation alone is sufficient to match a hardcoded interface, but the speed and duplex must also be explicitly configured.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

Common exam traps

Common exam trap: answer the scenario, not the keyword

Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.

Detailed technical explanation

How to think about this question

This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.
  • Use explanations to understand the rule behind the answer.

TExam Day Tips

  • Underline the problem statement mentally.
  • 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.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Real-world example

How this comes up in practice

A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.

What to study next

Got this wrong? Here's your next step.

Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

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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FAQ

Questions learners often ask

What does this 200-301 question test?

Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Configure speed 1000, duplex full, and no negotiation auto on Gi0/0, then replace the SFP-GE-SX with SFP-GE-L. — The CRC errors indicate a duplex mismatch or faulty medium. R1 is set to auto-negotiation while R2 is hardcoded to 1000/full, causing mismatch. First, set speed and duplex on R1 to match R2: 'speed 1000' and 'duplex full'. Also disable auto-negotiation with 'no negotiation auto'. The existing SFP-GE-SX only supports 550m, but the link requires 2 km; replace it with a 1000BASE-LX/LH SFP (SFP-GE-L) which supports up to 10 km. After changes, verify with 'show interfaces Gi0/0' to confirm no CRC errors and correct speed/duplex.

What should I do if I get this 200-301 question wrong?

Identify which 200-301 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jun 6, 2026

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