Question 1,231 of 2,152
MPLS L3VPNmediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the eBGP session between the PE and CE will be established successfully. This configuration is correct because the interface GigabitEthernet0/1 is placed into the VRF CUSTOMER-A with the ip vrf forwarding command, and the BGP neighbor 10.1.1.2 is correctly defined under the address-family ipv4 vrf CUSTOMER-A with a remote-as of 65001, which is a different AS than the PE’s 65000, making it an eBGP session. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how VRF-aware BGP separates routing tables and that the neighbor statement for a VRF must reside inside the VRF address-family block, not in the global BGP configuration. A common trap is assuming the neighbor must be defined globally first, but for eBGP under a VRF, the remote-as and activation are done solely within the address-family. Memory tip: “VRF neighbor lives in the VRF house”—the neighbor command for a VRF peer always goes under the address-family ipv4 vrf block.

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.

Examine the following partial configuration on a PE router:

interface GigabitEthernet0/1
 ip vrf forwarding CUSTOMER-A
 ip address 10.1.1.1 255.255.255.252

!

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

! address-family ipv4 vrf CUSTOMER-A

neighbor 10.1.1.2 remote-as 65001
  neighbor 10.1.1.2 activate

exit-address-family

What is the effect of this configuration?

Question 1mediummultiple choice
Open the full BGP breakdown →

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 eBGP session between PE and CE will be established successfully.

The configuration correctly assigns the interface to a VRF, then in BGP the neighbor under the VRF address-family is activated. However, the neighbor is directly connected on a /30 link, so a remote-as of 65001 is valid for an eBGP session. The configuration is correct and will establish an eBGP session with the CE router.

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 eBGP session between PE and CE will be established successfully.

    Why this is correct

    The VRF is defined, the interface is in the VRF, and the BGP neighbor is correctly configured under the VRF address-family. The neighbor IP is on the same subnet, so the eBGP session should come up.

    Related concept

    OSPF neighbours must agree on key parameters.

  • The BGP session will fail because the neighbor must be configured under the global BGP process.

    Why it's wrong here

    For VRF peers, the neighbor must be configured under the VRF address-family, not the global BGP process. This is correct.

  • The BGP session will fail because the neighbor remote-as must match the AS of the PE router.

    Why it's wrong here

    The CE router is in a different AS (65001), so eBGP is appropriate. The remote-as must match the CE's AS, which is 65001.

  • The BGP session will fail because the update-source is not specified for the VRF neighbor.

    Why it's wrong here

    The update-source is only needed for the iBGP session to the route reflector; the VRF neighbor uses the interface IP by default, which is correct.

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 300-410 OSPF questions on adjacency and route selection.

Related practice questions

Related 300-410 practice-question pages

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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: The eBGP session between PE and CE will be established successfully. — The configuration correctly assigns the interface to a VRF, then in BGP the neighbor under the VRF address-family is activated. However, the neighbor is directly connected on a /30 link, so a remote-as of 65001 is valid for an eBGP session. The configuration is correct and will establish an eBGP session with the CE router.

What should I do if I get this 300-410 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 300-410 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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Last reviewed: Jun 18, 2026

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