Question 1,180 of 2,152

MPLS L3VPN →hardMultiple SelectObjective-mapped

Quick Answer

The answer is to apply a route map with a 'match ip address' prefix-list to the VRF's import direction, or to remove the import route target that matches the remote site's export RT. These two methods work because MPLS L3VPN route selection on a PE router is governed by the VRF's import RTs and any inbound filtering; by either stripping the matching import RT or explicitly denying the specific prefixes via a route map, the local VRF will not install those remote site routes into its routing table. On the Cisco CCNP ENARSI 300-410 exam, this question tests your understanding of VRF route control and the distinction between import and export operations—a common trap is confusing the removal of the export RT (which controls outbound advertisement) with the import RT (which controls inbound learning). Remember the memory tip: "Import blocks what you take in; export blocks what you send out."

300-410 MPLS L3VPN Practice Question

This 300-410 practice question tests your understanding of mpls l3vpn. 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.

An engineer must prevent a VRF on a PE router from learning routes from a specific remote site in an MPLS L3VPN. Which TWO configuration changes on the local PE can achieve this? (Choose TWO.)

Question 1hardmulti select

Read the full MPLS explanation →

A
Remove the import RT that corresponds to the remote site's export RT from the VRF configuration.
Correct. Without a matching import RT, the PE will not install the remote site's VPNv4 routes into the VRF.
B
Remove the export RT from the VRF configuration.
Why wrong: Incorrect. The export RT controls how the local VRF's routes are advertised to other PEs, not what is received.
C
Apply a route map with a 'match ip address' prefix-list to the VRF's import direction to deny the remote site's prefixes.
Correct. A route map applied to the import direction can filter specific prefixes using a prefix-list.
D
Change the Route Distinguisher (RD) of the VRF to a different value.
Why wrong: Incorrect. The RD does not affect route filtering; it only makes prefixes unique.
E
Configure 'neighbor <remote-PE> default-originate' under the VRF address-family.
Why wrong: Incorrect. This command injects a default route, it does not filter specific 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

✓

Remove the import RT that corresponds to the remote site's export RT from the VRF configuration.

To block routes from a specific remote site, the engineer can either remove the import RT that matches the remote site's export RT, or configure a route map with a 'match ip address' clause to deny specific prefixes and apply it to the import direction. Removing the export RT from the local VRF would affect how the local site's routes are advertised, not what is received. Changing the RD does not affect route acceptance. The 'neighbor ... default-originate' command is unrelated to filtering VPNv4 routes.

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.

✓
Remove the import RT that corresponds to the remote site's export RT from the VRF configuration.
Why this is correct
Correct. Without a matching import RT, the PE will not install the remote site's VPNv4 routes into the VRF.
Related concept
OSPF neighbours must agree on key parameters.
✗
Remove the export RT from the VRF configuration.
Why it's wrong here
Incorrect. The export RT controls how the local VRF's routes are advertised to other PEs, not what is received.
✓
Apply a route map with a 'match ip address' prefix-list to the VRF's import direction to deny the remote site's prefixes.
Why this is correct
Correct. A route map applied to the import direction can filter specific prefixes using a prefix-list.
Related concept
OSPF neighbours must agree on key parameters.
✗
Change the Route Distinguisher (RD) of the VRF to a different value.
Why it's wrong here
Incorrect. The RD does not affect route filtering; it only makes prefixes unique.
✗
Configure 'neighbor <remote-PE> default-originate' under the VRF address-family.
Why it's wrong here
Incorrect. This command injects a default route, it does not filter specific 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.

Trap categories for this question

Command / output trap
Incorrect. This command injects a default route, it does not filter specific routes.

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 300-410 OSPF questions on adjacency and route selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

MPLS L3VPN — This question tests MPLS L3VPN — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: Remove the import RT that corresponds to the remote site's export RT from the VRF configuration. — To block routes from a specific remote site, the engineer can either remove the import RT that matches the remote site's export RT, or configure a route map with a 'match ip address' clause to deny specific prefixes and apply it to the import direction. Removing the export RT from the local VRF would affect how the local site's routes are advertised, not what is received. Changing the RD does not affect route acceptance. The 'neighbor ... default-originate' command is unrelated to filtering VPNv4 routes.

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

What is the key concept behind this question?

OSPF neighbours must agree on key parameters.

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