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

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iBGP multipath load sharing

Updated: February 28, 2026

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Overview

Describes iBGP multipath load sharing that installs multiple iBGP paths for the same destination, enabling load sharing to improve bandwidth utilization and network resiliency.

The iBGP multipath load sharing is a BGP capability that:

  • allows a router to install multiple iBGP paths to the same destination in the routing table,

  • enables load sharing across these eligible paths, and

  • improves network efficiency by leveraging path diversity.

By default, when a BGP router without a local policy receives multiple iBGP routes to the same destination, it selects only one best path and installs it in the routing table. With the iBGP multipath load sharing feature, the router can install multiple iBGP paths as best paths for the same destination, allowing traffic to be shared across these paths.

Feature Name Release Name Description
Share ECMP group between IPv4 and IPv6 routes based on RFC RFC5549 Release 25.4.1

Introduced in this release on: Modular Systems (8800 [ASIC: Q200])

The load-balancing objects (representing ECMP groups) are shared across IPv4 and IPv6 routes and this helps in saving hardware resources and improving convergence.

This stack uses IP BGP prefixes without any encapsulation where BGP next hops are directly connected.

Benefits of iBGP multipath load sharing

These are some of the benefits that iBGP multipath load sharing provides:

  • Increases bandwidth utilization by distributing traffic over multiple iBGP paths

  • Improves network resiliency and redundancy

  • Enhances path diversity, reducing the risk of single points of failure, and

  • Optimizes traffic flow and balances network load.

Restrictions for iBGP multipath load sharing

  • You cannot use per-VRF label mode with Carrier Supporting Carrier (CSC) networks that have both internal and external BGP multipath.

  • Do not use per-VRF label mode for BGP PIC edge with eBGP multipath, because it may cause routing loops. Use per-prefix label mode instead.

  • Per-VRF label mode does not support BGP best external within the same address family, as it can cause routing loops during network re-convergence.

Configure iBGP multipath load sharing

Enable iBGP multipath load sharing to use multiple iBGP paths for the same destination and improve load distribution.

Use this task to configure the maximum number of iBGP paths for load sharing in the BGP routing process.

Before you begin

  • Confirm you have the correct autonomous system (AS) number for your router.

  • Determine the required address family, IPv4 or IPv6, unicast or multicast.

  • Decide the maximum number of iBGP paths you want to configure.

Procedure

1.

Configure the AS number for your router.

Example:

Router# config
Router(config)# router bgp 100

Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGP routing process.

2.

Run the address-family {ipv4 |ipv6 } {unicast |multicast } command to enter the appropriate address family submode.

Example:

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

Run the maximum-paths ibgp number command to configures the maximum number of iBGP paths for load sharing.

Example:

Router(config-bgp-af)# maximum-paths ibgp 30
Router(config-bgp-af)# commit
4.

Verify the running configuration.

Example:

Router# show running-config
router bgp 100
 address-family ipv4 multicast
  maximum-paths ibgp 30
 !
!
end

This sample configuration uses 30 iBGP paths for load sharing.