mediumMultiple Choice
300-410 Practice Question: Examine this BGP configuration on router R3:…
Examine this BGP configuration on router R3:
router bgp 65001 neighbor 10.1.1.1 remote-as 65002
address-family ipv4
network 192.168.0.0 mask 255.255.252.0
aggregate-address 192.168.0.0 255.255.252.0 summary-only
What is the effect of the 'aggregate-address' command with the 'summary-only' keyword?
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
✓
It advertises the aggregate 192.168.0.0/22 and suppresses all more specific routes from being advertised to neighbor 10.1.1.1.
The aggregate-address command creates an aggregate route in BGP. The summary-only keyword suppresses more specific routes from being advertised.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It advertises the aggregate 192.168.0.0/22 and suppresses all more specific routes from being advertised to neighbor 10.1.1.1.
Why this is correct
The `summary-only` keyword suppresses all component routes within 192.168.0.0/22, so only the aggregate is advertised to neighbour 10.1.1.1. This satisfies the stem's requirement to reduce the BGP table by hiding more-specific prefixes while still announcing the summarised /22 to the remote AS 65002 peer.
- ✗
It advertises both the aggregate and all more specific routes.
Why it's wrong here
Summary-only suppresses the more specific routes when advertising to neighbours, so only the aggregate is sent. Advertising both is the behaviour without the keyword. It is tempting because aggregate-address alone does advertise both, but adding summary-only changes that behaviour specifically.
- ✗
It creates a static route for the aggregate.
Why it's wrong here
Aggregate-address is a BGP path-manipulation feature; it generates an aggregate entry in the BGP table from matching routes, not a static route in the routing table. It is tempting because the aggregate resembles a summary route, but no static route is created.
- ✗
It removes all more specific routes from the BGP table.
Why it's wrong here
Summary-only suppresses the more specific routes from advertisements to neighbours, but they remain in the local BGP table; the aggregate is installed alongside them. It is tempting because summary-only does hide specifics from peers, yet the RIB still holds them, so removal from the table is inaccurate.
Visual reference
Go deeper
Related to this question
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
Same concept, more angles
3 more ways this is tested on 300-410
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. Given this partial configuration on router R6: router bgp 65000 neighbor 192.168.1.1 remote-as 65001 address-family ipv4 network 172.16.0.0 mask 255.255.0.0 aggregate-address 172.16.0.0 255.255.0.0 What is missing if the administrator wants to ensure that only the aggregate route is advertised to neighbor 192.168.1.1?
medium- ✓ A.The 'summary-only' keyword is missing from the aggregate-address command.
- B.The 'network' command should be removed.
- C.The 'synchronization' command must be enabled.
- D.The 'neighbor 192.168.1.1 route-map' command is needed.
Why A: The 'aggregate-address' command without the 'summary-only' keyword advertises both the aggregate and the more-specific routes. To advertise only the aggregate, the 'summary-only' keyword must be added. The network statement is needed to inject the component route into BGP.
Variation 2. Which of the following best describes the behavior of BGP when an 'aggregate-address' command is used without the 'summary-only' keyword?
medium- ✓ A.The aggregate route is advertised, and all more specific routes are also advertised.
- B.Only the aggregate route is advertised.
- C.The aggregate route is not advertised unless a network command exists for it.
- D.The more specific routes are withdrawn from the BGP table.
Why A: Without the summary-only keyword, BGP advertises both the aggregate route and the more specific routes that are in the BGP table.
Variation 3. Which TWO statements about route summarization in BGP are true? (Choose TWO.)
medium- ✓ A.The 'aggregate-address' command creates a summary route in the BGP table.
- ✓ B.The 'summary-only' keyword can be used with 'aggregate-address' to suppress more specific routes.
- C.The 'network' command is used to create a summary route in BGP.
- D.BGP summarization requires a route-map to suppress more specific routes.
- E.Route summarization in BGP can only be configured on route reflectors.
Why A: Option A is correct because the Cisco IOS 'aggregate-address <prefix> <mask>' command under the BGP router configuration creates an aggregate (summary) entry in the BGP table, provided at least one more-specific route from the same AS exists in the BGP table. Option B is correct because adding the 'summary-only' keyword to 'aggregate-address' advertises only the aggregate and suppresses the more-specific component routes to all neighbors, which is the standard way to prevent the specifics from being advertised. Option C is wrong because the 'network' command injects an exact prefix into BGP (it does not perform summarization or create an aggregate). Option D is wrong because suppression of more-specifics is achieved with the 'summary-only' keyword (or with 'suppress-map' for selective suppression), not by a route-map requirement. Option E is wrong because route summarization via 'aggregate-address' can be configured on any BGP speaker, not only on route reflectors.
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.