Question 838 of 2,152

MPLS L3VPN →hardMultiple SelectObjective-mapped

Quick Answer

The correct answer identifies that the Route Distinguisher (RD) ensures overlapping IPv4 prefixes from different customers remain unique within the MPLS VPN network, and that a VPNv4 route is installed into the VRF routing table only when its Route Target (RT) matches an import RT configured in that VRF. This works because MP-BGP carries VPNv4 prefixes—formed by prepending the RD to the IPv4 prefix—between PE routers, while the import/export RT mechanism controls which routes are accepted into or advertised from a VRF. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how MPLS L3VPN isolates customer routing tables; a common trap is confusing the RD’s role in making prefixes unique with the RT’s role in controlling route distribution. Remember: the RD is for uniqueness, the RT is for import/export policy. A helpful memory tip is “RD keeps it unique, RT keeps it selective.”

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.

Which TWO statements about the interaction between MP-BGP and the VRF routing table in an MPLS L3VPN PE router are correct? (Choose TWO.)

Question 1hardmulti select

Open the full BGP breakdown →

A
A VPNv4 route received from a remote PE is installed in the VRF routing table only if its Route Target matches an import RT configured under the VRF.
Correct. The import RT controls which routes are accepted into the VRF.
B
The Route Distinguisher (RD) is automatically removed from the VPNv4 prefix before the route is placed into the VRF routing table.
Why wrong: Incorrect. The RD remains part of the VPNv4 prefix in the VRF; it is not removed. The VRF stores the full VPNv4 prefix (RD:IPv4).
C
When a PE originates a VPNv4 route, it uses the export RT of the VRF to tag the route, and the receiving PE uses the export RT to decide whether to accept the route.
Why wrong: Incorrect. The receiving PE uses its own import RT, not the export RT of the sender, to accept the route.
D
The next-hop of a VPNv4 route received from a remote PE is always changed to the local PE's loopback interface address before installation into the VRF.
Why wrong: Incorrect. The next-hop is not automatically changed; it remains the remote PE's address unless 'next-hop-self' is configured in the BGP address-family.
E
The Route Distinguisher (RD) ensures that overlapping IPv4 prefixes from different customers remain unique within the MPLS VPN network.
Correct. The RD makes prefixes unique across VRFs, allowing overlapping addresses.

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

✓

A VPNv4 route received from a remote PE is installed in the VRF routing table only if its Route Target matches an import RT configured under the VRF.

In MPLS L3VPN, MP-BGP (Multiprotocol BGP) is used to exchange VPNv4 routes between PE routers. The VRF routing table is populated via the 'import' and 'export' route target (RT) mechanism. The RD makes routes unique across VRFs. The correct statements are that a route is installed in the VRF routing table only if the received VPNv4 route's RT matches an import RT configured in the VRF, and that the RD is prepended to the IPv4 prefix to form a VPNv4 prefix. The incorrect statements describe wrong behaviors: the export RT is not used for receiving routes, the RD is not stripped before installation (it remains in the VRF as part of the prefix), and the next-hop is not changed to the PE's loopback by default unless 'next-hop-self' is configured.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
A VPNv4 route received from a remote PE is installed in the VRF routing table only if its Route Target matches an import RT configured under the VRF.
Why this is correct
Correct. The import RT controls which routes are accepted into the VRF.
Related concept
Static NAT maps one inside address to one outside address.
✗
The Route Distinguisher (RD) is automatically removed from the VPNv4 prefix before the route is placed into the VRF routing table.
Why it's wrong here
Incorrect. The RD remains part of the VPNv4 prefix in the VRF; it is not removed. The VRF stores the full VPNv4 prefix (RD:IPv4).
✗
When a PE originates a VPNv4 route, it uses the export RT of the VRF to tag the route, and the receiving PE uses the export RT to decide whether to accept the route.
Why it's wrong here
Incorrect. The receiving PE uses its own import RT, not the export RT of the sender, to accept the route.
✗
The next-hop of a VPNv4 route received from a remote PE is always changed to the local PE's loopback interface address before installation into the VRF.
Why it's wrong here
Incorrect. The next-hop is not automatically changed; it remains the remote PE's address unless 'next-hop-self' is configured in the BGP address-family.
✓
The Route Distinguisher (RD) ensures that overlapping IPv4 prefixes from different customers remain unique within the MPLS VPN network.
Why this is correct
Correct. The RD makes prefixes unique across VRFs, allowing overlapping addresses.
Related concept
Static NAT maps one inside address to one outside address.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Real-world example

How this comes up in practice

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

Got this wrong? Here's your next step.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this 300-410 question test?

MPLS L3VPN — This question tests MPLS L3VPN — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: A VPNv4 route received from a remote PE is installed in the VRF routing table only if its Route Target matches an import RT configured under the VRF. — In MPLS L3VPN, MP-BGP (Multiprotocol BGP) is used to exchange VPNv4 routes between PE routers. The VRF routing table is populated via the 'import' and 'export' route target (RT) mechanism. The RD makes routes unique across VRFs. The correct statements are that a route is installed in the VRF routing table only if the received VPNv4 route's RT matches an import RT configured in the VRF, and that the RD is prepended to the IPv4 prefix to form a VPNv4 prefix. The incorrect statements describe wrong behaviors: the export RT is not used for receiving routes, the RD is not stripped before installation (it remains in the VRF as part of the prefix), and the next-hop is not changed to the PE's loopback by default unless 'next-hop-self' is configured.

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

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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