mediumMultiple Choice
300-410 Practice Question: Consider the following configuration on a PE…
Consider the following configuration on a PE router:
ip vrf CUSTOMER-B
rd 100:1 route-target export 100:1 route-target import 100:2 !
interface GigabitEthernet0/2 ip vrf forwarding CUSTOMER-B ip address 192.168.2.1 255.255.255.252
What is the effect of this configuration?
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 PE will export routes from VRF CUSTOMER-B with RT 100:1 and import routes with RT 100:2.
The VRF has a route distinguisher and route-targets. The export RT is 100:1, meaning routes from this VRF are exported with that RT. The import RT is 100:2, so only routes with RT 100:2 are imported. This is a common setup for hub-and-spoke or inter-AS options.
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 PE will export routes from VRF CUSTOMER-B with RT 100:1 and import routes with RT 100:2.
Why this is correct
The route-target export 100:1 attaches RT 100:1 to routes leaving VRF CUSTOMER-B, while route-target import 100:2 accepts routes carrying RT 100:2 into that VRF. The route distinguisher 100:1 only makes prefixes unique, not controls import or export.
- ✗
The PE will export routes with RT 100:2 and import routes with RT 100:1.
Why it's wrong here
The export and import values are transposed: this VRF exports RT 100:1 and imports RT 100:2, as written. The reversal is tempting because both RTs appear in the configuration, so the direction of each statement is easily overlooked.
- ✗
The VRF will not work because the RD and RT must be identical.
Why it's wrong here
The RD and RT are independent fields: the RD only makes VPNv4 prefixes unique, while RTs control import and export into VRFs, so mismatched values are valid. The claim is tempting because both use the same 100:1 format, inviting the assumption they must match.
- ✗
The VRF will not work because route-target import and export must be configured under the BGP VRF address-family.
Why it's wrong here
Route targets are valid under the VRF definition and take effect without a BGP VRF address-family stanza; that stanza carries the RD for VPNv4 advertisement. The claim is tempting because MP-BGP is what actually transports the VPNv4 routes between PE routers.
Go deeper
Related to this question
Learn chapter
OSPF Route Summarization and Filtering
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
Key term
MP-BGP for VPN
MP-BGP for VPN is an extension of the Border Gateway Protocol that carries multiple types of network layer information to enable scalable, isolated virtual private networks over a shared provider infrastructure.
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Same concept, more angles
1 more way this is tested on 300-410
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Variation 1. Examine the following configuration on a PE router: ip vrf CUSTOMER-C rd 200:1 ! interface GigabitEthernet0/3 ip vrf forwarding CUSTOMER-C ip address 10.2.2.1 255.255.255.252 ! router ospf 1 vrf CUSTOMER-C network 10.2.2.0 0.0.0.3 area 0 ! router bgp 65000 address-family ipv4 vrf CUSTOMER-C redistribute ospf 1 exit-address-family What is missing from this configuration?
medium- ✓ A.The VRF is missing route-target export and import commands.
- B.The OSPF network command should use a wildcard mask of 0.0.0.0.
- C.The BGP neighbor must be configured under the VRF address-family.
- D.The VRF must have a route distinguisher that matches the route-target.
Why A: In MPLS L3VPN, a VRF requires route-target export and import commands to control the distribution of VPN routes via MP-BGP. Without these, the VRF cannot import or export routes, and the VPN will not function. The configuration shows a VRF with RD but no route-targets, so they are missing.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.