Question 275 of 2,152
SNMP TroubleshootinghardMultiple ChoiceObjective-mapped

Troubleshooting SNMP Polling in MPLS VPN VRF Environments

This 300-410 practice question tests your understanding of snmp troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.

Router R7 is part of an MPLS VPN network. It has multiple VRFs. The NMS is in the global routing table and needs to poll SNMP from devices in VRF BLUE. The configuration includes: snmp-server community public RO, snmp-server vrf BLUE community public RO. However, the NMS cannot poll the loopback interface of a router in VRF BLUE. The NMS can poll R7's global interfaces. What is the root cause?

Quick Answer

The root cause is that the NMS is trying to poll a device in VRF BLUE, but the SNMP agent on R7 is not configured to respond to SNMP requests for that VRF because the `snmp-server vrf` command is missing the `community` keyword or the VRF is not properly associated with the SNMP process. In MPLS VPN VRF environments, SNMP community strings are global by default, so the `snmp-server vrf BLUE community public RO` command is required to bind the community to the specific VRF; without it, the agent ignores SNMP requests arriving from the VRF’s context, even though the NMS has reachability to the loopback. This scenario tests your understanding of SNMP in MPLS VPN VRF troubleshooting for the Cisco CCNP ENARSI 300-410 exam, where a common trap is assuming that a global `snmp-server community` command covers all VRFs—it does not. Remember the memory tip: “VRF needs its own community command; global is blind to VRF traffic.”

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

The NMS is trying to poll a device in VRF BLUE, but the SNMP agent on R7 is not configured to respond to SNMP requests for that VRF because the 'snmp-server vrf' command is missing the 'community' keyword or the VRF is not properly associated with the SNMP process.

The NMS can poll global interfaces but not VRF BLUE interfaces because the SNMP agent on R7 is not properly configured to respond to SNMP requests for that VRF. The command 'snmp-server vrf BLUE community public RO' is correct, but the root cause is that the 'snmp-server vrf' command must be associated with the SNMP process, and if the VRF is not properly linked (e.g., missing the 'community' keyword or the VRF is not defined in the SNMP context), the agent will not process SNMP requests for that VRF. This isolates the VRF from SNMP polling, while global interfaces remain accessible.

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.

  • The NMS is trying to poll a device in VRF BLUE, but the SNMP agent on R7 is not configured to respond to SNMP requests for that VRF because the 'snmp-server vrf' command is missing the 'community' keyword or the VRF is not properly associated with the SNMP process.

    Why this is correct

    The 'snmp-server vrf BLUE community public RO' command is correct, but if the VRF is not defined or the interface is not in the VRF, SNMP may not respond. However, the most common issue is that the NMS's source IP is not in the VRF, so the SNMP agent uses the global routing table to respond, causing a mismatch.

    Related concept

    Read the scenario before looking for a memorised answer.

  • The loopback interface of the device in VRF BLUE is not advertised into the VRF's routing table.

    Why it's wrong here

    This would cause unreachability, but the NMS would not even get a response. The scenario says the NMS cannot poll, which could be due to routing, but the SNMP configuration is the key.

  • The SNMP community string 'public' is not allowed in VRF BLUE due to an ACL.

    Why it's wrong here

    No ACL is mentioned, and the 'snmp-server vrf' command does not include an ACL.

  • The NMS is using SNMPv3, but the VRF configuration only supports v2c.

    Why it's wrong here

    The configuration uses v2c community, and the NMS can poll global interfaces, so v3 is not the issue.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that simply adding 'snmp-server vrf <vrf-name>' is enough, but the trap is that the command must include the 'community' keyword to bind the community string to the VRF, or the VRF must be properly associated with the SNMP process via the 'snmp-server vrf' command without the community keyword only if a default community is already set, leading candidates to overlook the missing association.

Trap categories for this question

  • Command / output trap

    No ACL is mentioned, and the 'snmp-server vrf' command does not include an ACL.

  • Scenario analysis trap

    This would cause unreachability, but the NMS would not even get a response. The scenario says the NMS cannot poll, which could be due to routing, but the SNMP configuration is the key.

Detailed technical explanation

How to think about this question

In Cisco IOS, the 'snmp-server vrf <vrf-name>' command creates a separate SNMP context for that VRF, and the SNMP agent uses the VRF's routing table to respond to requests; if the VRF is not properly defined or the command is missing the 'community' keyword, the agent will not listen for SNMP requests on that VRF. This is because SNMP contexts isolate management traffic per VRF, and without explicit configuration, the agent defaults to the global routing table only. In real-world MPLS VPN networks, this misconfiguration is common when NMS systems need to poll devices in multiple VRFs, leading to silent failures where reachability exists but SNMP responses are not generated.

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.

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.

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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.

What to study next

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FAQ

Questions learners often ask

What does this 300-410 question test?

SNMP Troubleshooting — This question tests SNMP Troubleshooting — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The NMS is trying to poll a device in VRF BLUE, but the SNMP agent on R7 is not configured to respond to SNMP requests for that VRF because the 'snmp-server vrf' command is missing the 'community' keyword or the VRF is not properly associated with the SNMP process. — The NMS can poll global interfaces but not VRF BLUE interfaces because the SNMP agent on R7 is not properly configured to respond to SNMP requests for that VRF. The command 'snmp-server vrf BLUE community public RO' is correct, but the root cause is that the 'snmp-server vrf' command must be associated with the SNMP process, and if the VRF is not properly linked (e.g., missing the 'community' keyword or the VRF is not defined in the SNMP context), the agent will not process SNMP requests for that VRF. This isolates the VRF from SNMP polling, while global interfaces remain accessible.

What should I do if I get this 300-410 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jul 4, 2026

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