300-320 · Question #526
About BGP advertising route with using community, advertise to internet but not advertise to inside network
The correct answer is B. no-export. The BGP no-export well-known community tells receiving routers not to advertise those routes to any eBGP peers outside the AS (or outside a confederation sub-AS). Routes tagged no-export are shared with iBGP peers within the AS but are not propagated to external neighbors…
Question
About BGP advertising route with using community, advertise to internet but not advertise to inside network
Options
- Ano-advertise
- Bno-export
- Clocal-as
- Dinternet
How the community answered
(26 responses)- A12% (3)
- B81% (21)
- C4% (1)
- D4% (1)
Explanation
The BGP no-export well-known community tells receiving routers not to advertise those routes to any eBGP peers outside the AS (or outside a confederation sub-AS). Routes tagged no-export are shared with iBGP peers within the AS but are not propagated to external neighbors, effectively keeping them from crossing AS boundaries. The internet community allows unrestricted advertisement to all peers. no-advertise prevents advertisement to any peer at all. local-as restricts advertisement within a confederation sub-AS only.
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