notes: Outbound Route Filtering

- The purpose of outbound route filtering is to reduce the amount of BGP traffic and CPU use needed to process routing updates.
- With ORF routers exchange inbound filter configurations, which are used as outbound filters on neighboring routers.

ORF entries are part of the route refresh message.
- Negotiation of prefix-list ORF capability is done during BGP session setup.
- The side that has the prefix-list uses the 'send' option, and is configured with the prefix-list inbound.
- The side that sends the routes uses the 'receive' option.
- ORF requires the session to be reset after configured.
- Inbound route refresh is required, and only the inbound prefix-list filter is pushed to the neighbor and used by that neighbor the outbound direction.
- ORF-capable BGP speaker will install ORFs per neighbor.


commands:

- Enables negotiation of prefix-list ORF capability

router bgp 1

neighbor {ip} capability orf prefix-list {send|receive|both}

- Specifies the prefix that will be send to the ORF capable neighbor

neighbor {ip} prefix-list {name} in

- Useful dto verify neighbor capabilities

sh ip bgp neighbor

- Triggers a route refresh from ORF receivers
- [prefix-filter] option to refresh the remote filter

clear ip bgp {ip} in [prefix-filter]