The missing element is the `neighbor 192.168.1.1 send-community extended` command under the BGP address-family for the VRF. This command is essential because, in an MPLS L3VPN configuration, the BGP session between PE routers must be configured to exchange extended community attributes, which carry the route-target (RT) values that control VPN route import and export. Without this command, the router will advertise standard IPv4 routes instead of VPNv4 routes, and the remote PE will not install the prefixes into the correct VRF. On the ENCOR 350-401 exam, this is a classic trap: candidates often remember to configure the VRF, RD, and RT, but forget that the BGP neighbor statement must explicitly enable extended community exchange under the address-family. A reliable memory tip is to think "no community, no VPN"—if you see a working VRF configuration but routes are not being learned, always check for the missing `send-community extended` under the BGP address-family for the VRF.
CCNP 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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The BGP neighbor needs 'send-community extended' under the address-family to exchange VPN routes.
The configuration lacks the 'neighbor 192.168.1.1 send-community extended' command under the BGP address-family, which is required to exchange VPNv4 routes with extended communities.
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 BGP neighbor needs 'send-community extended' under the address-family to exchange VPN routes.
Why this is correct
Correct. Without 'send-community extended', the router will not send extended communities, which are essential for VPN route import/export.
The VRF definition is missing the 'mdt' command for multicast VPN.
Why it's wrong here
Incorrect. MDT is for MVPN, not required for basic L3VPN.
✗
The interface needs 'mpls ip' enabled for MPLS forwarding.
Why it's wrong here
Incorrect. MPLS forwarding is required on core-facing interfaces, not on the CE-facing interface.
✗
The BGP neighbor needs 'remote-as 65000' under the VRF address-family.
Why it's wrong here
Incorrect. The remote-as is already configured globally; it does not need to be repeated under the VRF.
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.
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 BGP neighbor needs 'send-community extended' under the address-family to exchange VPN routes. — The configuration lacks the 'neighbor 192.168.1.1 send-community extended' command under the BGP address-family, which is required to exchange VPNv4 routes with extended communities.
What should I do if I get this 350-401 question wrong?
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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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