Question 1,165 of 2,015

MPLS →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with address-family ipv4 vrf RED. This is because while the VRF is properly defined with a route distinguisher and route-target import/export values, and the interface is correctly bound to the VRF, the BGP process lacks the necessary address-family ipv4 vrf RED configuration to actually exchange customer routes within that VRF. On the ENCOR 350-401 exam, this scenario tests your understanding that defining a VRF and enabling VPNv4 peering with send-community extended is only half the setup; the missing piece is the VRF-specific address-family under BGP, which is a common trap where candidates assume the VPNv4 neighbor configuration alone handles all VRF routes. A reliable memory tip is "VRF needs its own BGP home" — every VRF requires its own address-family ipv4 vrf [name] under the BGP router to inject and redistribute its routes into the MPLS L3VPN.

350-401 MPLS Practice Question

This 350-401 practice question tests your understanding of mpls. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

ip vrf RED

rd 200:1 route-target export 200:1 route-target import 200:1 !

interface GigabitEthernet0/1
 ip vrf forwarding RED
 ip address 10.1.1.1 255.255.255.0

router bgp 65000
 neighbor 192.168.1.1 remote-as 65000
 neighbor 192.168.1.1 update-source Loopback0

address-family vpnv4

neighbor 192.168.1.1 activate
  neighbor 192.168.1.1 send-community extended

! Which statement about this configuration is true?

Question 1mediummultiple choice

Open the full BGP breakdown →

A
The configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with 'address-family ipv4 vrf RED'.
Correct. The VRF needs to be activated under BGP to advertise and receive VPN routes.
B
The 'send-community extended' command is unnecessary because it is enabled by default.
Why wrong: Incorrect. 'send-community extended' is not enabled by default; it must be explicitly configured.
C
The interface GigabitEthernet0/1 requires 'mpls ip' to forward MPLS packets.
Why wrong: Incorrect. The CE-facing interface does not need MPLS; MPLS is used on core-facing interfaces.
D
The VRF RED will automatically import routes from the VPNv4 address-family without additional configuration.
Why wrong: Incorrect. The VRF must be explicitly configured under BGP to import routes.

Full breakdown with real-world context →

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 configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with 'address-family ipv4 vrf RED'.

The BGP configuration includes 'send-community extended' under the VPNv4 address-family, which is required for MPLS L3VPN route exchange. However, the VRF RED is defined but not used in BGP.

Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

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 configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with 'address-family ipv4 vrf RED'.
Why this is correct
Correct. The VRF needs to be activated under BGP to advertise and receive VPN routes.
Related concept
OSPF neighbours must agree on key parameters.
✗
The 'send-community extended' command is unnecessary because it is enabled by default.
Why it's wrong here
Incorrect. 'send-community extended' is not enabled by default; it must be explicitly configured.
✗
The interface GigabitEthernet0/1 requires 'mpls ip' to forward MPLS packets.
Why it's wrong here
Incorrect. The CE-facing interface does not need MPLS; MPLS is used on core-facing interfaces.
✗
The VRF RED will automatically import routes from the VPNv4 address-family without additional configuration.
Why it's wrong here
Incorrect. The VRF must be explicitly configured under BGP to import routes.

Common exam traps

Common exam trap: OSPF can fail even when IP connectivity looks correct

OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.

Detailed technical explanation

How to think about this question

OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.

KKey Concepts to Remember

OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.

TExam Day Tips

Check area mismatch first when OSPF adjacency fails.
Review passive interfaces when a network is advertised but no neighbour forms.
Use show ip ospf neighbor and show ip route clues carefully.

Key takeaway

OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.

Real-world example

How this comes up in practice

A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.

What to study next

Got this wrong? Here's your next step.

Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 350-401 question test?

MPLS — This question tests MPLS — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The configuration is correct for MPLS L3VPN, but the VRF RED must also be configured under BGP with 'address-family ipv4 vrf RED'. — The BGP configuration includes 'send-community extended' under the VPNv4 address-family, which is required for MPLS L3VPN route exchange. However, the VRF RED is defined but not used in BGP.

What should I do if I get this 350-401 question wrong?

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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