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Cisco - What is BGP ORF (Outbound Route Filtering)?

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What is ORF?

Outbound Route Filtering (ORF) is a Cisco proprietary feature that prevents the unnecessary exchanging of routes that are subject to inbound filtering. This, in turn, minimizes bandwidth across the links and reduces CPU cycles upon the router during the processing of the neighbor UPDATE.

ORF works by the router transmitting its inbound filters to its neighbor, which the neighboring router then applies outbound.

Configuration

ORF is configured on a per-neighbor basis. In addition, both sides must be configured, as either the sender or receiver. In our example below, we are configuring only the ORF sender. 

router bgp 65001
  ...
neighbor 1.1.1.1 capability orf prefix-list send clear ip bgp 1.1.1.1 soft in