BGP Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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BGP Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

BGP full add-path reflection

Updated: June 9, 2026

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Describes how BGP full add-path reflection enables route reflectors to advertise all unique eligible paths to BGP peers, improving path visibility and network control.

BGP full add-path reflection is a BGP feature that

  • enables route reflectors to advertise all unique eligible BGP paths per prefix, including paths that have the same next hop but different BGP attributes

  • requires a route policy with the unique-nexthop-check-disable keyword for additional-path selection or Optimal Route Reflection (ORR), and

  • suppresses advertisement of exact duplicate paths, with identical next hop and attributes, to optimize efficiency.

BGP full add-path reflection is especially beneficial when migrating from iBGP full mesh to route reflector architectures, as it preserves path transparency and operational fidelity for troubleshooting and network analysis.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

BGP full add-path reflection

Release 26.3.1

Introduced in this release on: Fixed Systems (8200 [ASIC: Q100, Q200, P100], 8700 [ASIC: P100, K100], 8010 [ASIC: A100]); Centralized Systems (8600); Modular Systems (8800 [LC ASIC: Q100, Q200, P100])

You gain full visibility into all unique eligible BGP paths per prefix as route reflectors can now advertise multiple unique paths, not just one per next hop. This enables more informed routing and traffic engineering, with exact duplicate paths still suppressed.

Comparison of default BGP route reflector behavior and full add-path reflection

This table contrasts default BGP route reflector behavior and full add-path reflection.

Table 2. BGP route reflector: Default vs. full add-path reflection

Attribute

Default behavior

Full add-path reflection

Path advertisement per prefix

One path per unique next hop

All eligible non-identical paths

Duplicate path suppression

Yes

Yes

Configuration requirement

None (default)

Route policy containing unique-nexthop-check-disable, referenced by additional-path selection or associated with an ORR configuration
Tip

Enable BGP full add-path reflection only when you require explicit path diversity or enhanced visibility. Default suppression is typically sufficient for smaller or less complex environments.

Benefits of BGP full add-path reflection

The main benefits of BGP full add-path reflection include:

  • support for advanced use cases such as multi-path routing and deterministic traffic engineering

  • improved troubleshooting with end-to-end path visibility, and

  • efficient scaling by suppressing true duplicates without persistent database changes.

Guidelines for deploying BGP full add-path reflection

  • The feature is not enabled by default and must be configured in a path selection route-policy.

  • Suppression of exact duplicate paths is always enforced.

  • BGP full add-path reflection is most advantageous in large-scale or complex topologies where client path diversity is needed.

How BGP full add-path reflection works

BGP full add-path reflection is a route reflector feature that modifies how eligible BGP paths are advertised to downstream peers in order to improve path visibility and network control.

  • Enable the feature by referencing a route policy containing the unique-nexthop-check-disable keyword from additional-path selection, or by associating the route policy with an Optimal Route Reflection (ORR) configuration, as applicable.

  • Advertise only non-identical eligible paths. A path is considered a duplicate if both the next hop and all BGP attributes are identical.

  • Disable full add-path reflection by removing the unique-nexthop-check-disable keyword from the route policy. This restores the default unique-next-hop check, limiting path advertisement to one eligible path per unique next hop.

Summary

BGP full add-path reflection allows downstream peers to receive all unique eligible paths per prefix, improving topology visibility and supporting advanced routing choices, while duplicate suppression maintains efficient updates.

The key components involved in the operation of BGP full add-path reflection are:

  • Operator (You): Adds or removes the unique-nexthop-check-disable keyword in the route policy referenced by additional-path selection or associated with an ORR configuration to enable or disable full add-path reflection.

  • Route reflector: Uses the configured additional-path selection or ORR policy to evaluate eligible BGP paths, suppress identical duplicates, and advertise the resulting unique paths.

  • BGP peers: Receive the eligible paths advertised by the route reflector, subject to the applicable address-family and add-path configuration.

Workflow

These stages describe the operational flow of BGP full add-path reflection from configuration to peer path reception:

  1. You enable or disable full add-path reflection by adding or removing the unique-nexthop-check-disable keyword in the route policy used for path selection.

    For additional-path operation, the route policy is referenced by the additional-path selection configuration for the applicable address family. For ORR operation, the route policy is associated with the ORR configuration, which is then applied to the applicable address family.

  2. The route reflector updates its path-selection processing according to the modified additional-path or ORR policy. Current and new BGP paths evaluated through that policy use the corresponding full add-path reflection behavior.

  3. The route reflector receives BGP updates. For each prefix, it applies standard eligibility checks, path-selection rules, and the configured policy to identify candidate paths for advertisement.

    Redundant or ECMP network designs can provide multiple eligible paths for the same prefix. When full add-path reflection is enabled, paths are not excluded solely because they have the same next hop. Paths with the same next hop remain eligible when their BGP attributes differ.

  4. The route reflector suppresses identical duplicate paths. Two paths are duplicates when both their next hop and all their BGP attributes are identical. Only one identical path is retained for advertisement.

    Duplicate suppression maintains control-plane efficiency by preventing redundant updates. This check is performed regardless of whether full add-path reflection is enabled.

  5. The route reflector advertises the resulting unique eligible paths for each prefix. For additional-path operation, paths are advertised to downstream peers for which add-path advertisement is configured and negotiated. For ORR operation, paths are advertised according to the applied ORR configuration and its associated route policy.

  6. Downstream BGP peers receive the advertised paths as permitted by their capabilities and address-family configuration. They perform local path selection and routing according to their policies and engineering requirements.

Result

Enabling BGP full add-path reflection allows downstream peers to receive all unique, eligible BGP paths. This supports improved routing decisions, advanced traffic engineering, and easier troubleshooting.

Configure BGP full add-path reflection

Configure BGP full add-path reflection on a route reflector to advertise all unique eligible BGP paths to downstream peers, increasing BGP path visibility and supporting advanced routing policies.

  • Enables path diversity for enhanced traffic engineering and troubleshooting capabilities.

BGP full add-path reflection provides a route reflector with the ability to advertise every unique, eligible BGP path to its clients. This extends path visibility and selection in route reflector-based BGP designs. Without this feature, only one path per unique next hop is typically advertised. Activating full add-path reflection supports efficient control plane operation and more granular routing choices.

  • Enable this feature by including the unique-nexthop-check-disable keyword in a route policy and referencing the policy from additional-path selection or associating it with an Optimal Route Reflection (ORR) configuration. The route policy is not applied directly to a neighbor or peer group.

Before you begin

Before you begin, ensure the following prerequisites are satisfied:

  • BGP is configured and operational on the route reflector.

  • The address families requiring full add-path reflection are identified.

  • For additional-path operation, the downstream peers support the BGP additional-path capability.

Follow these steps to configure BGP full add-path reflection on a route reflector:

Procedure

  1. Define or edit a route policy to control BGP path selection.

    Example:

    Router# configure
Router(config)# route-policy <path-selection-policy-name>
Router(config-rpl)#

  2. Configure the route policy to select all eligible paths and disable the unique-next-hop check.

    Example:

    Router(config-rpl)# set path-selection all advertise unique-nexthop-check-disable
Router(config-rpl)# end-policy

    Insert this statement in the appropriate section of the route policy.

  3. Reference the route policy from additional-path selection or associate it with an ORR configuration, as applicable.

    Example:

    For additional-path selection:

    Router(config)# router bgp <asn>
Router(config-bgp)# address-family ipv4 unicast
Router(config-bgp-af)# additional-paths receive
Router(config-bgp-af)# additional-paths send
Router(config-bgp-af)# additional-paths selection route-policy <path-selection-policy-name>
Router(config-bgp-af)# commit

    For ORR:

    Router(config)# router bgp <asn>
Router(config-bgp)# optimal-route-reflection ipv4 <orr-group-name> <orr-next-hop-address> route-policy <path-selection-policy-name>
Router(config-bgp)# address-family ipv4 unicast
Router(config-bgp-af)# optimal-route-reflection apply <orr-group-name>
Router(config-bgp-af)# commit

    • For additional-path operation, configure the send and receive capabilities as required for the deployment.

    • For ORR operation, use a route policy that contains the unique-nexthop-check-disable keyword when you define the ORR configuration, and then apply the ORR configuration under the applicable address family.

  4. Verify that the route policy contains the full add-path reflection action.

    Example:

    Router# show running-config route-policy <path-selection-policy-name>

    Ensure that unique-nexthop-check-disable appears in the route-policy output.

  5. Verify that the route policy is referenced by the applicable path-selection configuration.

    Example:

    Router# show running-config router bgp

    For additional-path operation, confirm that the policy is referenced by additional-path selection under the applicable address family. For ORR operation, confirm that the policy is associated with the ORR configuration and that the ORR configuration is applied under the applicable address family.

  6. Verify that all unique eligible paths are advertised correctly.

    Example:

    Router# show bgp neighbors <client-ip> advertised-routes

    Confirm that the expected unique eligible BGP paths are advertised to downstream peers. Paths with the same next hop can be advertised when their BGP attributes differ, but paths with an identical next hop and identical BGP attributes are suppressed as duplicates.