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

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Soft reconfiguration

Updated: February 28, 2026

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Overview

Details BGP soft reconfiguration concepts and demonstrates how to configure BGP soft reconfiguration for a neighbor, supporting inbound policy changes without renegotiating BGP sessions.

A soft reconfiguration is a BGP feature that

  • stores inbound routing updates received from a neighbor

  • enables policy changes to be applied without clearing the BGP session, and

  • provides the ability to reapply or review routing policies on previously received routes.

How the soft-reconfiguration inbound command works

When the soft-reconfiguration inbound command is configured for a BGP neighbor, the router stores the original, unmodified BGP paths received from that neighbor. If the neighbor supports route refresh, a route refresh request can be sent to retrieve routing information. If route refresh is not supported, soft reconfiguration ensures that all received routes are available locally for policy reapplication.

Conditions for storing BGP routes during soft reconfiguration

  • Storing updates from a neighbor is possible only if either the neighbor supports route refresh or the soft-reconfiguration inbound command is configured.

  • The soft-reconfiguration inbound always command forces the router to store a copy of the received routes even if route refresh is supported by the neighbor.

Memory considerations for soft reconfiguration

Soft reconfiguration is memory intensive, as all received paths must be stored until they are no longer needed.

Suppose a BGP router has received multiple routing updates from a neighbor. If network administrators need to change routing policies or filters, soft reconfiguration allows them to reapply new policy rules to previously stored routes without resetting the BGP session or losing any routing updates.

Configure BGP soft reconfiguration for a neighbor

Enable BGP to store incoming route updates from a neighbor, allowing policy changes to be applied with a soft clear instead of resetting the BGP session.

Use soft reconfiguration when a BGP neighbor does not support route refresh, or when you require the flexibility to apply new policies and retrieve original routes without a full session reset.

Before you begin

  • Identify the autonomous system (AS) number.

  • Obtain the IP address of the BGP neighbor.

  • Ensure sufficient memory is available, as soft reconfiguration can be resource-intensive.

Procedure

Enter BGP configuration mode, and enable soft reconfiguration for the neighbor.

Example:

Router(config)# router bgp 120 
Router(config-bgp)# neighbor 172.16.40.24
Router(config-bgp-nbr)# address-family ipv4 unicast
Router(config-bgp-nbr-af)# soft-reconfiguration inbound always