300-420 · Question #165
Refer to the exhibit. AS65533 and AS65530 are announcing a partial Internet routing table as well as their IP subnets. An architect must create a design that ensures AS64512 become a transit AS…
The correct answer is D. no-export. The architect needs to configure AS64512 to function as a transit AS, ensuring that routes learned from its peers are appropriately filtered for onward advertisement to other external ASs.
Question
Refer to the exhibit. AS65533 and AS65530 are announcing a partial Internet routing table as well as their IP subnets. An architect must create a design that ensures AS64512 become a transit AS. Which filtering solution must the architect choose?
Exhibit
Options
- AMaximum-prefix
- BNo-advertise
- CNext-hop
- Dno-export
How the community answered
(37 responses)- A14% (5)
- B3% (1)
- C11% (4)
- D73% (27)
Why each option
The architect needs to configure AS64512 to function as a transit AS, ensuring that routes learned from its peers are appropriately filtered for onward advertisement to other external ASs.
`Maximum-prefix` is used to limit the number of prefixes accepted from a BGP peer, protecting the router from routing table overflow, and does not control transit behavior or route propagation policies.
The `no-advertise` BGP community attribute prevents a route from being advertised to any other BGP peer, whether internal or external, which is a more restrictive action than typically desired for a transit AS.
Modifying the `next-hop` attribute affects how traffic reaches a destination but is not a filtering solution that controls whether routes are propagated to make an AS a transit network.
The `no-export` BGP community attribute prevents routes tagged with it from being advertised outside of the local AS, which is essential for a transit AS to control route propagation and ensure routes remain within its boundary when necessary.
Concept tested: BGP community for route propagation control
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16-10/bgp-xe-16-10-book/bgp-route-maps-comm-attr.html
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