The answer is that the route is functioning correctly, as the output shows a valid BGP route for 10.20.20.0/24 within the VRF CUSTOMER_B. The key to interpreting this show ip route vrf output is recognizing that the code "B" indicates a BGP-learned route, and the administrative distance of 20 confirms it is an external BGP (eBGP) route, which is perfectly normal and operational. On the Cisco CCNP ENARSI 300-410 exam, this type of question tests your ability to quickly read VRF route table output and distinguish between actual problems and healthy routing states—a common trap is assuming any route with a high administrative distance or specific metric is flawed, when in fact eBGP routes typically have an AD of 20 and a metric of 0. Remember, a valid route entry with a next-hop IP, an age timestamp, and no error flags means the routing is working as intended. A useful memory tip: "B 20/0 is a BGP go" — if you see BGP with AD 20 and metric 0, the route is good to go.
300-410 MPLS L3VPN Practice Question
This 300-410 practice question tests your understanding of mpls l3vpn. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
A network engineer runs the following command on Router CE1:
CE1# show ip route vrf CUSTOMER_B 10.20.20.0 24
Routing Table: CUSTOMER_B
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/24 is subnetted, 1 subnets
B 10.20.20.0 [20/0] via 10.1.1.2, 00:02:34
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route is functioning correctly.
The output shows a BGP route for 10.20.20.0/24 in VRF CUSTOMER_B. The route is learned via BGP with an administrative distance of 20, which is typical for external BGP. The route is valid. No problem is evident.
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 route is not being installed in the routing table.
Why it's wrong here
The route is present with 'B' code, indicating it is installed.
The VRF name appears in the output, and the route is present.
✗
The next hop is unreachable.
Why it's wrong here
The output does not show any indication of unreachability; the route is active.
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
The VRF name appears in the output, and the route is present.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
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.
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 route is functioning correctly. — The output shows a BGP route for 10.20.20.0/24 in VRF CUSTOMER_B. The route is learned via BGP with an administrative distance of 20, which is typical for external BGP. The route is valid. No problem is evident.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer runs the following command on Router PE2:
PE2# show ip bgp vpnv4 vrf CUSTOMER_A 10.10.10.0 24
BGP routing table entry for 10.10.10.0/24, version 15
Paths: (1 available, best #1, table CUSTOMER_A)
Advertised to update-groups:
1
Refresh Epoch 1
Local, imported path from 10.10.10.0/24
10.1.1.1 (metric 20) from 10.1.1.1 (10.1.1.1)
Origin incomplete, metric 0, localpref 100, valid, internal, best
Extended Community: RT:100:100
mpls labels in/out 18/19
Based on this output, what is the problem?
medium
A.The route is not being advertised to any BGP peer.
B.The route is missing the required Route Target community.
✓ C.The route is functioning correctly with no issues.
D.The route has an incorrect label binding.
Why C: The output shows a VPNv4 route for VRF CUSTOMER_A. The route is marked as 'imported path from 10.10.10.0/24', which indicates it was imported from the global table or another VRF. The route is valid and best, with labels assigned. No problem is indicated; the route is functioning correctly.
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