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

High-scale BGP Multipath and Load Balancing

Updated: February 28, 2026

Overview

Describes advanced BGP multipath and load balancing techniques that enhance network scalability and efficiency by supporting up to 1,024 ECMPs or 256 UCMPs through hierarchical load balancing and multipath configurations including 64-way, 128-way, and 256-way ECMP.

You will learn how high-scale BGP multipath and load balancing improve network scalability and efficiency.

High-scale BGP multipath and load balancing refers to advanced networking features that

enable routers to distribute traffic across multiple paths to a destination
support configurations for various Equal Cost Multipath (ECMP) levels, including 64-way, 128-way, and 256-way ECMP
introduce hierarchical load balancing for even greater scalability, supporting up to 1,024 ECMPs or 256 Unequal Cost Multipath (UCMP) paths, and
are crucial for high-traffic networks where efficient load balancing is necessary to optimize bandwidth utilization and improve network performance.

You can leverage ECMP with these scaling options:

64-way ECMP configures up to 64 equal-cost next hops and load balances traffic over up to 64 LSPs.
128-way ECMP allows the routers to configure up to 128 ECMP next hops for BGP (iBGP/eBGP) in IPv4/IPv6 and support 64 IGP multipaths.
256-way ECMP configures up to 256 next hops for ECMP in IPv4/IPv6 and optimizes network bandwidth by load balancing traffic across parallel paths.
Hierarchical load balancing model expands ECMP scalability beyond hardware limitations by splitting routes.

64-way multipath ECMP

Describes the support for up to 64 equal-cost multipath next hops in BGP and the ability to load balance traffic over multiple LSPs to increase bandwidth utilization.

128-way multipath ECMP

Explains the capability to configure up to 128 ECMP next hops for BGP in IPv4 and IPv6, supporting parallel multipaths for both BGP and IGP, with guidelines and restrictions for deployment.

256-way multipath ECMP

Describes the support for up to 256 ECMP next hops in BGP for IPv4 and IPv6, optimizing bandwidth by load balancing traffic across parallel paths with associated restrictions.

Hierarchical load balancing

Explains hierarchical load balancing that expands ECMP and UCMP scalability beyond hardware limits by splitting routes into multiple hierarchical levels, requiring CEF enabled on all routers.

Need help?

Open a support case

(Requires a Cisco Service Contract)

The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.