The answer is that the prefix 192.168.100.0/24 is denied because the BGP update carries the no-export community, and an inbound route-map or filter on the router is configured to reject routes with that community. This occurs because the no-export community is a well-known BGP community that tells the receiving router not to advertise the prefix to any eBGP peers; however, in this debug output, the router itself is denying the update upon receipt, meaning a local policy explicitly blocks routes tagged with no-export. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret debug ip bgp updates output and understand how community-based filtering works—a common trap is confusing the no-export community’s propagation restriction with an inbound denial, which is actually caused by a configured filter. Remember the memory tip: “no-export stops the export, but a filter stops the import.”
300-410 Route Maps and Route Filtering Practice Question
This 300-410 practice question tests your understanding of route maps and route filtering. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 to troubleshoot a route filtering issue:
R1# debug ip bgp updates
BGP(0): 10.1.1.2 rcvd UPDATE w/ attr: nexthop 10.1.1.2, origin i, metric 0, path 65001 65002
BGP(0): 10.1.1.2 rcvd UPDATE about 192.168.100.0/24 -- DENIED due to: community no-export;
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The prefix 192.168.100.0/24 is denied because of the no-export community.
The debug output shows that BGP received an update for prefix 192.168.100.0/24 from neighbor 10.1.1.2, but the update was denied because the prefix has the community 'no-export'. This indicates that an inbound route-map or filter is configured to deny routes with the no-export community.
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 prefix 192.168.100.0/24 is being accepted and installed in the BGP table.
Why it's wrong here
The output clearly states 'DENIED due to: community no-export', so the route is not accepted.
✓
The prefix 192.168.100.0/24 is denied because of the no-export community.
Why this is correct
The debug output explicitly shows that the update is denied due to the no-export community.
The prefix 192.168.100.0/24 is denied because of an AS_PATH filter.
Why it's wrong here
The denial reason is community no-export, not AS_PATH.
✗
The prefix 192.168.100.0/24 is accepted but not advertised to any neighbor.
Why it's wrong here
The route is denied and not installed in the BGP table.
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 output clearly states 'DENIED due to: community no-export', so the route is not accepted.
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.
Route Maps and Route Filtering — This question tests Route Maps and Route Filtering — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The prefix 192.168.100.0/24 is denied because of the no-export community. — The debug output shows that BGP received an update for prefix 192.168.100.0/24 from neighbor 10.1.1.2, but the update was denied because the prefix has the community 'no-export'. This indicates that an inbound route-map or filter is configured to deny routes with the no-export community.
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 to verify BGP route filtering:
R1# show bgp ipv4 unicast 192.168.1.0/24
BGP routing table entry for 192.168.1.0/24, version 2
Paths: (1 available, best #1, table default)
Advertised to update-groups:
1
Refresh Epoch 1
Local, (received & used)
10.1.1.2 (metric 20) from 10.1.1.2 (2.2.2.2)
Origin IGP, metric 0, localpref 100, valid, internal, best
rx pathid: 0, tx pathid: 0x0
Community: no-export
What does the 'Community: no-export' indicate?
easy
A.The route will not be advertised to any iBGP peers.
✓ B.The route will not be advertised to any eBGP peers.
C.The route is filtered by an inbound route-map.
D.The route is not installed in the routing table.
Why B: The community 'no-export' indicates that this route should not be advertised to any eBGP peers. This is a well-known community that controls route propagation.
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Question Discussion
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