hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Runs the following command on Router R1: R1# show…
A network engineer runs the following command on Router R1:
R1# show ip bgp neighbors 10.1.1.2 advertised-routes
BGP table version is 10, local router ID is 10.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path *> 10.10.10.0/24 0.0.0.0 0 32768 i *> 10.20.20.0/24 0.0.0.0 0 32768 i
R1# show route-map
route-map BLOCK_RFC1918, permit, sequence 10 Match clauses:
ip address prefix-list RFC1918
Set clauses: Policy routing matches: 0 packets, 0 bytes route-map BLOCK_RFC1918, deny, sequence 20 Match clauses: Set clauses: Policy routing matches: 0 packets, 0 bytes
R1# show ip prefix-list RFC1918 ip prefix-list RFC1918: 3 entries
seq 5 deny 10.0.0.0/8 le 32 seq
10 deny 172.16.0.0/12 le 32
seq
15 deny 192.168.0.0/16 le 32
seq
20 permit 0.0.0.0/0 le 32
Based on this output, what is the most likely issue?
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 route-map BLOCK_RFC1918 is not applied to the BGP neighbor, so RFC 1918 routes are being advertised.
The route-map BLOCK_RFC1918 is applied to filter routes, but the advertised routes include 10.10.10.0/24 and 10.20.20.0/24, which are RFC 1918 addresses. The prefix-list RFC1918 should deny these, but the route-map is not being applied to the BGP neighbor, so routes are not filtered. The correct answer is that the route-map is not applied to the BGP neighbor.
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-map BLOCK_RFC1918 is not applied to the BGP neighbor, so RFC 1918 routes are being advertised.
Why this is correct
The prefix-list denies RFC 1918, but the route-map is not applied to the neighbor, so routes are advertised.
- ✗
The prefix-list RFC1918 is misconfigured and permits all routes.
Why it's wrong here
The prefix-list denies RFC 1918 and permits others.
- ✗
The route-map is applied but the match clause is incorrect.
Why it's wrong here
The match clause references the prefix-list correctly.
- ✗
The BGP session is not established.
Why it's wrong here
Routes are being advertised, so session is up.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
BGP Prefix Filtering
BGP Prefix Filtering is the practice of controlling which network routes (prefixes) a router accepts or advertises to its BGP neighbors, preventing unwanted or harmful routes from spreading across the internet.
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Variation 1. A network engineer runs the following command on Router R1: R1# show ip bgp neighbors 192.168.1.2 advertised-routes BGP table version is 14, local router ID is 10.1.1.1 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, x best-external, a additional-path, c RIB-compressed, Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric LocPrf Weight Path *> 10.10.10.0/24 192.168.1.2 0 0 65001 i *> 10.20.20.0/24 192.168.1.2 0 0 65001 i Total number of prefixes 2 Based on this output, what is a likely issue?
hard- ✓ A.The neighbor 192.168.1.2 is not receiving all routes because a route-map is filtering them.
- B.The BGP session is down because there are no prefixes advertised.
- C.The router is not receiving updates from its peers.
- D.The prefix-list is misconfigured and blocking all routes.
Why A: The output shows only two prefixes advertised to the neighbor, but the network likely has more routes. The route-map applied to the neighbor may be filtering routes. The correct answer identifies that a route-map is likely filtering out other prefixes.
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.