- Cisco BGP Overview
- BGP 4
- Configuring a Basic BGP Network
- BGP Support for 4-byte ASN
- IPv6 Routing: Multiprotocol BGP Extensions for IPv6
- IPv6 Routing: Multiprotocol BGP Link-Local Address Peering
- IPv6 Multicast Address Family Support for Multiprotocol BGP
- Connecting to a Service Provider Using External BGP
- BGP Named Community Lists
- BGP Prefix-Based Outbound Route Filtering
- BGP Route-Map Continue Support for Outbound Policy
- Removing Private AS Numbers from the AS Path in BGP
- Configuring BGP Neighbor Session Options
- BGP Neighbor Policy
- BGP Dynamic Neighbors
- BGP Support for Next-Hop Address Tracking
- BGP Restart Neighbor Session After Max-Prefix Limit Reached
- BGP Support for Dual AS Configuration for Network AS Migrations
- Configuring Internal BGP Features
- BGP VPLS Auto Discovery Support on Route Reflector
- BGP NSF Awareness
- IPv6 NSF and Graceful Restart for MP-BGP IPv6 Address Family
- BGP Support for BFD
- BGP Support for MTR
- BGP Link Bandwidth
- iBGP Multipath Load Sharing
- BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN
- Loadsharing IP Packets Over More Than Six Parallel Paths
- BGP Policy Accounting
- BGP Policy Accounting Output Interface Accounting
- BGP Cost Community
- BGP Support for IP Prefix Import from Global Table into a VRF Table
- BGP Support for IP Prefix Export from a VRF Table into the Global Table
- BGP per Neighbor SoO Configuration
- Per-VRF Assignment of BGP Router ID
- BGP Next Hop Unchanged
- BGP Event-Based VPN Import
- BGP Best External
- BGP PIC Edge for IP and MPLS-VPN
- Configuring BGP: RT Constrained Route Distribution
- Configuring BGP Consistency Checker
- BGP MIB Support
- Cisco-BGP-MIBv2
- BGP Additional Paths
- BGP Attribute Filter and Enhanced Attribute Error Handling
- BGP—Support for iBGP Local-AS
- BGP-Multiple Cluster IDs
- BGP-RT and VPN Distinguisher Attribute Rewrite Wildcard
- BGP-VPN Distinguisher Attribute
- BGP-VRF-Aware Conditional Advertisement
- BGP Diverse Path Using a Diverse-Path Route Reflector
- BGP Graceful Shutdown
- Finding Feature Information
- Information About BGP Prefix-Based Outbound Route Filtering
- How to Configure BGP Prefix-Based Outbound Route Filtering
- Configuration Examples for BGP Prefix-Based Outbound Route Filtering
- Additional References
- Feature Information for BGP Prefix-Based Outbound Route Filtering
BGP Prefix-Based Outbound Route Filtering
The BGP Prefix-Based Outbound Route Filtering (ORF) feature uses BGP ORF send and receive capabilities to minimize the number of BGP updates that are sent between BGP peers. Configuring this feature can help reduce the amount of system resources required for generating and processing routing updates by filtering out unwanted routing updates at the source. For example, this feature can be used to reduce the amount of processing required on a router that is not accepting full routes from a service provider network.
- Finding Feature Information
- Information About BGP Prefix-Based Outbound Route Filtering
- How to Configure BGP Prefix-Based Outbound Route Filtering
- Configuration Examples for BGP Prefix-Based Outbound Route Filtering
- Additional References
- Feature Information for BGP Prefix-Based Outbound Route Filtering
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Information About BGP Prefix-Based Outbound Route Filtering
BGP Prefix-Based Outbound Route Filtering
BGP prefix-based outbound route filtering uses the BGP ORF send and receive capabilities to minimize the number of BGP updates that are sent between BGP peers. Configuring BGP ORF can help reduce the amount of system resources required for generating and processing routing updates by filtering out unwanted routing updates at the source. For example, BGP ORF can be used to reduce the amount of processing required on a router that is not accepting full routes from a service provider network.
The BGP prefix-based outbound route filtering is enabled through the advertisement of ORF capabilities to peer routers. The advertisement of the ORF capability indicates that a BGP peer 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 can be configured with send 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 requested with the clear ip bgp in prefix-filter command or after an ORF prefix list with immediate status is processed. The BGP peer will continue to apply the inbound prefix list to received updates after the local peer pushes the inbound prefix list to the remote peer.
How to Configure BGP Prefix-Based Outbound Route Filtering
Filtering Outbound Routes Based on BGP Prefix
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.
1.
enable
2.
configure
terminal
3.
ip
prefix-list
list-name
[seq
seq-value] {deny
network
/
length |
permit
network
/
length} [ge
ge-value] [le
le-value]
4.
router
bgp
autonomous-system-number
5.
address-family
ipv4
[unicast |
multicast |
vrf
vrf-name]
6.
neighbor
{ip-address |
peer-group-name}
remote-as
autonomous-system-number
7.
neighbor
ip-address
ebgp-multihop
[hop-count]
8.
neighbor
ip-address
capability
orf
prefix-list
[send |
receive |
both]
9.
neighbor
{ip-address |
peer-group-name}
prefix-list
prefix-list-name {in |
out}
10.
end
11.
clear
ip
bgp
{ip-address |
*}
in
prefix-filter
DETAILED STEPS
Configuration Examples for BGP Prefix-Based Outbound Route Filtering
Example: Influencing Outbound Path Selection
The following example creates an outbound route filter and configures Router A (10.1.1.1) to advertise the filter to Router-B (172.16.1.2). An IP prefix list named FILTER is created to specify the 192.168.1.0/24 subnet for outbound route filtering. The ORF send capability is configured on Router A so that Router A can advertise the outbound route filter to Router B.
Router A Configuration (Sender)
ip prefix-list FILTER seq 10 permit 192.168.1.0/24 ! router bgp 65100 address-family ipv4 unicast neighbor 172.16.1.2 remote-as 65200 neighbor 172.16.1.2 ebgp-multihop neighbor 172.16.1.2 capability orf prefix-list send neighbor 172.16.1.2 prefix-list FILTER in end
Router B Configuration (Receiver)
The following example configures Router B to advertise the ORF receive capability to Router A. Router B will install the outbound route filter, defined in the FILTER prefix list, after ORF capabilities have been exchanged. An inbound soft reset is initiated on Router B at the end of this configuration to activate the outbound route filter.
router bgp 65200 address-family ipv4 unicast neighbor 10.1.1.1 remote-as 65100 neighbor 10.1.1.1 ebgp-multihop 255 neighbor 10.1.1.1 capability orf prefix-list receive end clear ip bgp 10.1.1.1 in prefix-filter
The following example shows how the route map named set-as-path is applied to outbound updates to the neighbor 10.69.232.70. The route map will prepend the autonomous system path “65100 65100” to routes that pass access list 1. The second part of the route map is to permit the advertisement of other routes.
router bgp 65100 network 172.16.0.0 network 172.17.0.0 neighbor 10.69.232.70 remote-as 65200 neighbor 10.69.232.70 route-map set-as-path out ! route-map set-as-path 10 permit match address 1 set as-path prepend 65100 65100 ! route-map set-as-path 20 permit match address 2 ! access-list 1 permit 172.16.0.0 0.0.255.255 access-list 1 permit 172.17.0.0 0.0.255.255 ! access-list 2 permit 0.0.0.0 255.255.255.255
Additional References
Related Documents
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
BGP commands |
Standards and RFCs
Standard/RFC |
Title |
---|---|
RFC 2918 |
Route Refresh Capability for BGP-4 |
Technical Assistance
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for BGP Prefix-Based Outbound Route Filtering
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to . An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
---|---|---|
BGP Prefix-Based Outbound Route Filtering |
The BGP Prefix-Based Outbound Route Filtering feature uses BGP ORF send and receive capabilities to minimize the number of BGP updates that are sent between BGP peers. Configuring this feature can help reduce the amount of system resources required for generating and processing routing updates by filtering out unwanted routing updates at the source. For example, this feature can be used to reduce the amount of processing required on a router that is not accepting full routes from a service provider network. |