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 path reflection

Updated: June 9, 2026

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

BGP full path reflection is a BGP feature that

  • enables route reflectors to advertise all eligible, non-identical BGP paths per unique next hop to clients

  • requires explicit configuration using the unique-nexthop-check-disable keyword in a route-policy, and

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

BGP full 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 path reflection

Release 26.3.1

You gain full visibility into all 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 path reflection

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

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

Attribute

Default behavior

Full 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)

Explicit route-policy with unique-nexthop-check-disable
Tip

Enable BGP full 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 path reflection

The main benefits of BGP full 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 path reflection

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

  • Suppression of exact duplicate paths is always enforced.

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

How BGP full path reflection works

BGP full 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 applying a route-policy with the unique-nexthop-check-disable keyword to a BGP peer or peer group.

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

  • Deactivate the feature by removing the route-policy keyword, which returns the route reflector to the default behavior of advertising one path per unique next hop.

Summary

BGP full 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 feature is quickly reversible by removing the enabling policy.

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

  • Operator (You): Applies or removes the route-policy to enable or disable full path reflection for selected BGP peers.

  • Route reflector: Applies the policy, evaluates BGP path updates, suppresses duplicates, and advertises unique eligible paths.

  • BGP peers: Receive all unique, eligible paths from the route reflector for each prefix.

Workflow

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

  1. You apply or remove a route-policy with set path-selection all advertise unique-nexthop-check-disable under the BGP process for relevant neighbors or peer groups. Perform this in router configuration mode and attach the policy to the required address family. This immediately activates or deactivates the full path reflection logic on the route reflector.
  2. The route reflector updates processing to use the new path selection policy for affected neighbors. All current and new BGP updates for peers with the policy now use full path reflection logic. This ensures consistent path advertisement handling based on your configuration.
  3. The route reflector receives BGP updates. For each prefix, it applies standard path selection and policy logic to identify all eligible paths. This stage identifies candidate paths for duplicate suppression before advertisement.
    Note

    Redundant or ECMP network designs often provide multiple eligible paths per prefix.

  4. The route reflector suppresses duplicate paths. Two paths are duplicates if the next hop and all attributes are identical. Only one is retained for advertisement. Duplicate suppression ensures control-plane efficiency and protocol correctness. This check is performed irrespective of whether full path reflection is enabled.
  5. The route reflector advertises all unique eligible paths per prefix to each downstream BGP peer with the policy applied. Peers receive the complete set of unique eligible paths as allowed by their address family configuration. This stage increases visibility and enables flexible routing strategies in the network.
  6. BGP peers receive the unique paths and use them for local path selection and routing according to their policies or engineering needs. Peers may use multipath, load balancing, or perform enhanced troubleshooting with the additional path information. The network benefits from improved path visibility and greater control.

Result

Enabling BGP full 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 path reflection

Configure BGP full path reflection on a route reflector to advertise all 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 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 path reflection supports efficient control plane operation and more granular routing choices.

  • This feature is enabled by including the unique-nexthop-check-disable keyword in a route-policy that is applied to outbound BGP neighbors.

Before you begin

Before you begin, ensure the following prerequisites are satisfied:

  • BGP is configured and operational on the route reflector.

  • The list of BGP neighbors and specific address families requiring full path reflection is identified.

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

Procedure

1.

Define or edit a route-policy to control BGP path advertisement.

Example:

Router# configure
Router(config)# route-policy <add-path-policy-name>
Router(config-rpl)#
2.

Enable the route reflector to advertise all eligible, unique BGP paths to clients using the unique-nexthop-check-disable keyword to the route-policy.

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.

Apply the route-policy add-path to each BGP neighbor or peer group within the desired address-family.

Example:


Router(config)# router bgp <asn>
Router(config-bgp)# neighbor-group <rr-clients>
Router(config-bgp-nbrgrp)#address-family ipv4 unicast
Router(config-bgp-nbrgrp-af)# additional-paths send
Router(config-bgp-nbrgrp-af)#route-policy <add-path-policy-name> add-path
Router(config-bgp-nbrgrp-af)# commit

  • This step activates full path reflection for the specified BGP peers.

  • Repeat for additional neighbor groups or address families if required.
4.

Verify that full path reflection is active.

Example:

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

Ensure unique-nexthop-check-disable appears in the route-policy output.
5.

Verify that all eligible paths are advertised correctly.

Example:

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

Confirm that all eligible, unique BGP paths are being advertised to downstream peers, and check that the route-policy is applied. Validate multiple non-duplicate paths in the advertised paths output.