Quick Answer
The correct conclusion is that VRF CUSTOMER-A uses RD 65000:1 and is associated with GigabitEthernet0/0.100, as directly confirmed by the show vrf brief command. This output explicitly lists each VRF name, its Route Distinguisher, and the interfaces mapped to it, providing a clear verification of VRF interface mapping. On the ENCOR 350-401 exam, this tests your ability to interpret show commands for MPLS L3VPN path isolation, where a common trap is assuming the show ip interface brief output alone reveals VRF membership—it does not, as that command only shows interface status and IP addresses. Instead, you must cross-reference with show vrf brief to confirm which interface belongs to which VRF. A helpful memory tip: remember that “show vrf brief” is your VRF-to-interface cheat sheet, while “show ip interface brief” is just a status snapshot—always pair them to verify mapping.
This 350-401 practice question tests your understanding of vrf and path isolation. 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 R5:
R5# show ip interface brief | include VRF Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0.100 10.0.0.1 YES NVRAM up up GigabitEthernet0/0.200 10.0.1.1 YES NVRAM up up GigabitEthernet0/0.300 10.0.2.1 YES NVRAM up up Loopback100 10.100.0.1 YES NVRAM up up
R5# show vrf brief
Name Default RD Protocols Interfaces CUSTOMER-A 65000:1 ipv4 Gi0/0.100 CUSTOMER-B 65000:2 ipv4 Gi0/0.200 CUSTOMER-C 65000:3 ipv4 Gi0/0.300
Based on this output, what can be concluded?
All interfaces belong to the same VRF
Why wrong: Each subinterface is in a different VRF.
VRF CUSTOMER-A uses RD 65000:1 and is associated with GigabitEthernet0/0.100
The output shows CUSTOMER-A with RD 65000:1 and interface Gi0/0.100.
Loopback100 is in VRF CUSTOMER-C
Why wrong: Loopback100 is not listed in any VRF in the vrf brief output.
There is no VRF configured on Router R5
Why wrong: Three VRFs are clearly listed.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VRF CUSTOMER-A uses RD 65000:1 and is associated with GigabitEthernet0/0.100
Option B is correct because the 'show vrf brief' output explicitly lists CUSTOMER-A with Route Distinguisher (RD) 65000:1 and its associated interface GigabitEthernet0/0.100. This confirms the VRF configuration and the interface-to-VRF mapping, which is fundamental for MPLS L3VPN path isolation.
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.
All interfaces belong to the same VRF
Why it's wrong here
Each subinterface is in a different VRF.
VRF CUSTOMER-A uses RD 65000:1 and is associated with GigabitEthernet0/0.100
Why this is correct
The output shows CUSTOMER-A with RD 65000:1 and interface Gi0/0.100.
Related concept
Read the scenario before looking for a memorised answer.
Loopback100 is in VRF CUSTOMER-C
Why it's wrong here
Loopback100 is not listed in any VRF in the vrf brief output.
There is no VRF configured on Router R5
Why it's wrong here
Three VRFs are clearly listed.
Common exam traps
Cisco often tests the misconception that the 'show ip interface brief | include VRF' command displays VRF membership, when in fact it only filters lines containing the string 'VRF' (which may not appear in the output), leading candidates to incorrectly conclude no VRFs exist or that all interfaces share a single VRF.
Trap categories for this question
Command / output trap
Loopback100 is not listed in any VRF in the vrf brief output.
Detailed technical explanation
VRFs (Virtual Routing and Forwarding) create separate routing tables on a single router, using Route Distinguishers (RDs) to make overlapping customer IP prefixes unique. The 'show ip interface brief | include VRF' command filters interfaces with 'VRF' in their status, but here it shows all interfaces because the filter string 'VRF' does not match any output line; the actual VRF-to-interface mapping is confirmed via 'show vrf brief'. In real-world deployments, VRFs are critical for MPLS L3VPN services, allowing service providers to isolate customer traffic without requiring separate physical routers.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
VRF and Path Isolation — This question tests VRF and Path Isolation — Read the scenario before looking for a memorised answer..
The correct answer is: VRF CUSTOMER-A uses RD 65000:1 and is associated with GigabitEthernet0/0.100 — Option B is correct because the 'show vrf brief' output explicitly lists CUSTOMER-A with Route Distinguisher (RD) 65000:1 and its associated interface GigabitEthernet0/0.100. This confirms the VRF configuration and the interface-to-VRF mapping, which is fundamental for MPLS L3VPN path isolation.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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