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

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Delay BGP route advertisements

Updated: February 28, 2026

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Overview

Explains the benefits of delaying BGP route advertisements until the RIB and FIB are synchronized, helping prevent traffic loss during start-up and allowing operators to control route propagation with a configurable delay interval.

Delay BGP route advertisements is a BGP feature that

  • prevents traffic loss by delaying BGP update generation until the Routing Information Base (RIB) is synchronized with the Forwarding Information Base (FIB)

  • defers route advertisements during BGP start-up to avoid premature propagation, and

  • allows a configurable delay from 1 to 600 seconds.

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Delay BGP Route Advertisements

 Release 25.4.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*)

*This feature is supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A

  • 8011-12G12X4Y-D

Delay BGP Route Advertisements

 Release 25.1.1

Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*)

*This feature is supported on:

  • 8712-MOD-M

  • 8011-4G24Y4H-I

Delay BGP Route Advertisements

 Release 24.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*)

*This feature is supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 88-LC1-36EH

  • 88-LC1-12TH24FH-E

  • 88-LC1-52Y8H-EM

Delay BGP Route Advertisements

 Release 7.5.3

You can now prevent traffic loss due to premature advertising of BGP routes and subsequent packet loss in a network. You can achieve this by setting the delay time of the BGP start-up in the router until the Routing Information Base (RIB) is synchronized with the Forward Information Base (FIB) in the routing table. This delays the BGP update generation and prevents traffic loss in a network.

You can configure a minimum delay of 1 second and a maximum delay of 600 seconds.

This feature introduces the update wait-install delay startup command.

When BGP forwards traffic, it waits for feedback from the Routing Information Base (RIB) until the RIB is ready to forward traffic. After the RIB is ready, BGP sends the route updates to the BGP neighbors and peer-groups. Advertising routes before the RIB is synchronized with the Forwarding Information Base (FIB) can cause traffic loss. To avoid this problem, the router must delay the BGP start-up process to delay the BGP route update generation until the RIB and FIB are synchronized.

To accomplish this, you can configure the update wait-install delay startup command to delay BGP update generation. This feature allows you to configure the minimum and maximum delay periods. Use the show bgp process command to view the BGP process delay since the last router reload. Set the delay to 1 to 600 seconds to prevent traffic loss.

Restrictions of delay BGP route advertisements

This feature is applicable only for the following Address Family Indicators (AFIs):

  • IPv4 unicast

  • IPv6 unicast

  • VPNv4 unicast

  • VPNv6 unicast

Configure BGP route advertisement delay

Delay BGP update generation until the Routing Information Base (RIB) is synchronized, preventing premature route advertisements and traffic loss.

Configure a start-up delay for the desired address family, IPv4, IPv6, VPNv4, or VPNv6, using the BGP address-family submode.

Before you begin

  • Determine the BGP autonomous system number.

  • Identify the address family to configure.

  • Choose the delay value in seconds.

Procedure

1.

Specify the BGP autonomous system number and enter BGP configuration mode.

Example:

Router# configure
Router(config)# router bgp 1
2.

Specify the address-family.

Example:

Router(config-bgp)# address-family ipv4 unicast
3.

Schedule the delay of the BGP process to prevent routes from being advertised to peers until RIB is synchronized.

Example:

Router(config-bgp-af)# update wait-install delay startup 10
Router(config-bgp-af)# commit
4.

Verify the running configuration.

Example:

Router# show running-config router bgp 1
router bgp 1
 address-family ipv4 unicast
  update wait-install delay startup 10
!
5.

Run the show bgp process command to verify the delay of the BGP process update since the last router reload.

Example:

Router# show bgp process

BGP Process Information:
BGP is operating in STANDALONE mode
Autonomous System number format: ASPLAIN
Autonomous System: 100
Router ID: 192.168.0.2 (manually configured)
Default Cluster ID: 192.168.0.2
Active Cluster IDs:  192.168.0.2
------------------------------
------------------------------
Update wait-install enabled:
  ack request 2, ack rcvd 2, slow ack 0
  startup delay 10 secs

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