Quick Answer
The answer is that the ifIndex for Loopback0 is 3. This is correct because the output of the show snmp mib ifmib ifindex command directly displays the SNMP ifIndex-to-interface mapping, where each interface is assigned a unique numeric identifier used by SNMP managers for monitoring and polling. In the provided output, Loopback0 is explicitly listed with ifIndex 3, confirming the mapping. On the Cisco CCNP ENARSI 300-410 exam, this command tests your understanding of SNMP interface indexing and how it differs from interface numbering—a common trap is assuming ifIndex values are sequential or match the interface number, but as shown, Tunnel0 jumps to ifIndex 10. Remember that ifIndex values are assigned dynamically and can be non-contiguous, so always read the output carefully rather than guessing. A helpful memory tip: ifIndex is like a social security number for each interface—unique, but not in order.
This 300-410 practice question tests your understanding of snmp troubleshooting. 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.
A network engineer runs the following command on Router R1:
R1# show snmp mib ifmib ifindex
ifIndex: 1
Interface: GigabitEthernet0/0
Description: GigabitEthernet0/0
ifIndex: 2
Interface: GigabitEthernet0/1
Description: GigabitEthernet0/1
ifIndex: 3
Interface: Loopback0
Description: Loopback0
ifIndex: 10
Interface: Tunnel0
Description: Tunnel0
Based on this output, which statement is correct?
The ifIndex for Loopback0 is 3.
The output clearly shows Loopback0 with ifIndex 3.
The ifIndex values are assigned sequentially starting from 0.
Why wrong: The ifIndex values start from 1 and are not necessarily sequential (note the jump to 10).
GigabitEthernet0/0 has ifIndex 2.
Why wrong: GigabitEthernet0/0 has ifIndex 1.
Tunnel0 has ifIndex 3.
Why wrong: Tunnel0 has ifIndex 10.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The ifIndex for Loopback0 is 3.
The output shows the mapping between SNMP ifIndex values and interface names. The ifIndex values are not sequential (1,2,3,10), which is normal. The Tunnel0 interface has ifIndex 10. This mapping is used by SNMP managers to identify interfaces.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The ifIndex for Loopback0 is 3.
Why this is correct
The output clearly shows Loopback0 with ifIndex 3.
Related concept
Read the scenario before looking for a memorised answer.
The ifIndex values are assigned sequentially starting from 0.
Why it's wrong here
The ifIndex values start from 1 and are not necessarily sequential (note the jump to 10).
GigabitEthernet0/0 has ifIndex 2.
Why it's wrong here
GigabitEthernet0/0 has ifIndex 1.
Tunnel0 has ifIndex 3.
Why it's wrong here
Tunnel0 has ifIndex 10.
Common exam traps
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
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 300-410 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
Identify which 300-410 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.
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FAQ
SNMP Troubleshooting — This question tests SNMP Troubleshooting — Read the scenario before looking for a memorised answer..
The correct answer is: The ifIndex for Loopback0 is 3. — The output shows the mapping between SNMP ifIndex values and interface names. The ifIndex values are not sequential (1,2,3,10), which is normal. The Tunnel0 interface has ifIndex 10. This mapping is used by SNMP managers to identify interfaces.
Identify which 300-410 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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 18, 2026
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