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Routing & Switching · Intermediate

BGP Community

An optional transitive 32-bit BGP attribute (often written AS:value) used to tag routes for policy decisions.

Definition

Communities let providers and customers signal intent, such as setting local preference, blackholing or regional filtering. Well-known communities include NO_EXPORT, NO_ADVERTISE, NO_EXPORT_SUBCONFED (LOCAL_AS) and BLACKHOLE. Cisco requires send-community per neighbor and ip bgp-community new-format for AS:NN display.

Example

set community 65001:100 additive

Exam tip

Cisco IOS does not send communities until neighbor send-community is configured.

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