для Cisco Cisco IOS Software Release 12.2(14)S
BGP Prefix-Based Outbound Route Filtering
How to Configure BGP Prefix-Based Outbound Route Filtering
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Cisco IOS Release 12.0(11)ST, 12.2(4)T, 12.2(14)S, and 12.0(22)S
Enabling BGP Prefix-Based Outbound Route Filtering
The BGP Prefix-Based Outbound Route Filtering feature is enabled through the advertisement of ORF
capabilities to peer routers. The advertisement of the ORF capability indicates that a BGP speaker will
accept a prefix list from a neighbor and apply the prefix list to locally configured ORFs (if any exist).
When this capability is enabled, the BGP speaker can install the inbound prefix list filter to the remote
peer as an outbound filter, which reduces unwanted routing updates.
capabilities to peer routers. The advertisement of the ORF capability indicates that a BGP speaker will
accept a prefix list from a neighbor and apply the prefix list to locally configured ORFs (if any exist).
When this capability is enabled, the BGP speaker can install the inbound prefix list filter to the remote
peer as an outbound filter, which reduces unwanted routing updates.
The BGP Prefix-Based Outbound Route Filtering feature can be configured with send and/or receive
ORF capabilities. The local peer advertises the ORF capability in send mode. The remote peer receives
the ORF capability in receive mode and applies the filter as an outbound policy. The local and remote
peers exchange updates to maintain the ORF on each router. Updates are exchanged between peer routers
by address family depending on the ORF prefix list capability that is advertised. The remote peer starts
sending updates to the local peer after a route refresh has been configured with the clear ip bgp
command or after an ORF prefix list with immediate status is processed. The BGP speaker will continue
to apply the inbound prefix list to received updates after the speaker pushes the inbound prefix list to the
remote peer.
ORF capabilities. The local peer advertises the ORF capability in send mode. The remote peer receives
the ORF capability in receive mode and applies the filter as an outbound policy. The local and remote
peers exchange updates to maintain the ORF on each router. Updates are exchanged between peer routers
by address family depending on the ORF prefix list capability that is advertised. The remote peer starts
sending updates to the local peer after a route refresh has been configured with the clear ip bgp
command or after an ORF prefix list with immediate status is processed. The BGP speaker will continue
to apply the inbound prefix list to received updates after the speaker pushes the inbound prefix list to the
remote peer.
Benefits of BGP Prefix-Based Outbound Route Filtering
The BGP Prefix-Based Outbound Route Filtering feature can limit the number of unwanted routing
updates, which will reduce the amount of resources required for routing update generation and
processing. This feature also reduces the amount of resources required to receive and discard routes that
would otherwise be filtered out.
updates, which will reduce the amount of resources required for routing update generation and
processing. This feature also reduces the amount of resources required to receive and discard routes that
would otherwise be filtered out.
How to Configure BGP Prefix-Based Outbound Route Filtering
This section contains the following procedures:
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Configuring BGP Prefix-Based Outbound Route Filtering
The BGP Prefix-Based Outbound Route Filtering supports prefix length matching, wild-card based
prefix matching, and exact address prefix matching for address family support. This feature can be
configured on a router to send or receive ORF capabilities with either the send or receive keywords. This
feature can also be configured on a router to both send and receive ORF capabilities with the both
keyword.
prefix matching, and exact address prefix matching for address family support. This feature can be
configured on a router to send or receive ORF capabilities with either the send or receive keywords. This
feature can also be configured on a router to both send and receive ORF capabilities with the both
keyword.
Prerequisites
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BGP peering sessions must be established, and BGP ORF capabilities must be enabled on each
participating router before prefix-based ORF announcements can be received.
participating router before prefix-based ORF announcements can be received.
Restrictions
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The BGP Prefix-Based Outbound Route Filtering feature does not support multicast.