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

128-way multipath ECMP

Updated: February 28, 2026

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Overview

Restrictions for 128-way multipath ECMP
Configure 128-multipath ECMP

Overview

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.

The 128-way multipath ECMP is a BGP feature that

enables the router to support up to 128 BGP and 64 Interior Gateway Protocol (IGP) parallel multipaths to a destination
enables you to configure up to 128 ECMP next hops for BGP in IPv4 and IPv6 on Cisco 8000 Series Routers, and
allows up to 128-path ECMP in the global table for BGP, specifically for iBGP and eBGP prefixes.

Table 1. Feature History Table
Feature Name	Release Name	Description
128-way ECMP	Release 25.4.1	Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only) This feature is now supported on: 8011-32Y8L2H2FH 8011-12G12X4Y-A 8011-12G12X4Y-D
128-way ECMP	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
128-way ECMP	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
128-way ECMP	Release 7.3.1	This feature enables the router to support up to 128 BGP and 64 IGP parallel multipath routes to a destination.

Restrictions for 128-way multipath ECMP

These restrictions apply to the 128-way multipath ECMP feature:

Virtual Routing and Forwarding (VRF) and global routing tables in IGP support 64-path ECMP as the maximum for paths, with up to 128 paths supported when backup is configured.
BGP and IGP in UCMP support 64-path ECMP.
Label Distribution Protocol (LDP) receives support for only 64-way ECMP from the Routing Information Base (RIB). As a result, Label Switch Database (LSD) receives a maximum of 64 equal-cost multipaths from all clients.

Configure 128-multipath ECMP

Configure 128-multipath ECMP for iBGP, eBGP, or eiBGP to enable traffic load balancing across multiple paths.

You can configure eBGP and iBGP multipath to function together. However, if eiBGP multipath is already configured, you cannot configure iBGP or eBGP multipath.

Procedure

Configure 128-multipath ECMP for the desired BGP type, iBGP, eBGP, or eiBGP.

Configure 128-multipath ECMP in iBGP.

Router(config)#router bgp 100
Router(config-bgp)#bgp router-id 10.10.10.11 
Router(config-bgp)#address-family ipv4 unicast 
Router(config-bgp-af)#maximum-paths ibgp 128 
Router(config-bgp-af)#exit
Router(config-bgp)#address-family ipv6 unicast 
Router(config-bgp-af)#maximum-paths ibgp 128 
Router(config-bgp-af)#commit

Running configuration:

Router# show run router bgp
router bgp 100
bgp router-id 10.10.10.11 address-family ipv4 unicast
maximum-paths ibgp 128
!
address-family ipv6 unicast maximum-paths ibgp 128

Configure 128-multipath ECMP in eBGP.

Router(config)#router bgp 100
Router(config-bgp)#bgp router-id 10.10.10.11 
Router(config-bgp)#address-family ipv4 unicast 
Router(config-bgp-af)#maximum-paths ebgp 128 
Router(config-bgp-af)#exit
Router(config-bgp)#address-family ipv6 unicast 
Router(config-bgp-af)#maximum-paths ebgp 128 
Router(config-bgp-af)#commit

Running configuration:

Router# show run router bgp
router bgp 100
bgp router-id 10.10.10.11 address-family ipv4 unicast
maximum-paths ebgp 128
!
address-family ipv6 unicast maximum-paths ebgp 128

Configure 128-multipath ECMP in eiBGP.

Router(config)#router bgp 100
Router(config-bgp)#bgp router-id 10.10.10.11 
Router(config-bgp)#address-family ipv4 unicast 
Router(config-bgp-af)#maximum-paths eibgp 128 
Router(config-bgp-af)#exit
Router(config-bgp)#address-family ipv6 unicast 
Router(config-bgp-af)#maximum-paths eibgp 128 
Router(config-bgp-af)#commit

Running configuration:

Router# show run router bgp
router bgp 100
bgp router-id 10.10.10.11 address-family ipv4 unicast
maximum-paths eibgp 128
!
address-family ipv6 unicast maximum-paths eibgp 128

Verify the BGP multipath marking in the routing table, FIB, and RIB, and confirm the total number of IPv4 and IPv6 ECMP paths, as well as the platform's ECMP capabilities.

Verify the BGP multipath marking.

Example:

Router# show bgp 192.0.2.254/24

BGP routing table entry for 191.1.0.0/24 Versions:
Process	bRIB/RIB SendTblVer
Speaker	11008	11008
Last Modified: Aug 14 13:59:39.403 for 00:00:05
Paths: (35 available, best #1)
Advertised IPv4 Unicast paths to peers (in unique update groups): 100.101.3.2
Path #1: Received by speaker 0
Advertised IPv4 Unicast paths to peers (in unique update groups): 100.101.3.2
Local, (received & used)
120.0.101.1 from 120.0.101.1 (120.0.101.1)
Origin IGP, localpref 100, valid, internal, best, group-best, multipath Received Path ID 0, Local Path ID 1, version 7708
Path #2: Received by speaker 0
Advertised IPv4 Unicast paths to peers (in unique update groups): 100.101.3.2
Local, (received & used)
120.0.102.1 from 120.0.102.1 (120.0.102.1)
Origin IGP, localpref 100, valid, internal, multipath Received Path ID 0, Local Path ID 6, version 11008
........
Path #128: Received by speaker 0
Advertised IPv4 Unicast paths to peers (in unique update groups): 100.101.3.2
Local, (received & used)


120.0.227.1 from 120.0.227.1 (120.0.227.1)
Origin IGP, localpref 100, valid, internal, multipath Received Path ID 0, Local Path ID 6, version 14008

Verify the BGP multipath marking in FIB.

Example:

Router# show cef 192.0.2.254/24
191.1.0.0/24, version 46115, internal 0x5000001 0x40 (ptr 0xd236928) [1], 0x0 (0xe715668), 0x0 (0x0)
Updated Aug 14 13:59:39.007
Prefix Len 24, traffic index 0, precedence n/a, priority 4
via 120.0.101.1/32, 3 dependencies, recursive, bgp-multipath [flags 0x6080] path-idx 0 NHID 0x0 [0xd236a00 0x0]
next hop 120.0.101.1/32 via 120.0.101.1/32
via 120.0.102.1/32, 3 dependencies, recursive, bgp-multipath [flags 0x6080] path-idx 1 NHID 0x0 [0xde9a6d0 0x0]
next hop 120.0.102.1/32 via 120.0.102.1/32
via 120.0.103.1/32, 3 dependencies, recursive, bgp-multipath [flags 0x6080] path-idx 2 NHID 0x0 [0xde9a010 0x0]
….
via 120.0.227.1/32, 3 dependencies, recursive, bgp-multipath [flags 0x6080] path-idx 127 NHID 0x0 [0xde9a010 0x0]

Verify the BGP multipath marking in RIB.

Example:

Router# show route 192.0.2.254/24

Routing entry for 191.1.0.0/24
Known via "bgp 1", distance 200, metric 0, type internal Installed Aug 14 13:59:38.971 for 00:11:48
Routing Descriptor Blocks
120.0.101.1, from 120.0.101.1, BGP multi path Route metric is 0
120.0.102.1, from 120.0.102.1, BGP multi path Route metric is 0
…
120.0.227.1, from 120.0.227.1, BGP multi path Route metric is 0

Verify the total number of IPv4 ECMP paths.

Example:

Router# show bgp ipv4 unicast 191.1.0.0/24 | i multipath | utility wc -l
128

Verify the total number of IPv6 ECMP paths.

Example:

Router# show bgp ipv6 unicast 191:1::/64 | i multipath | utility wc -l
128

Verify the IPv4 128-multipath ECMP.

Example:

Router# show route ipv4 191.1.0.0/24 | i multipath | utility wc -l
128
Router# show cef ipv4 191.1.0.0/24 | i multipath | utility wc -l
128

Verify the IPv6 128-multipath ECMP.

Example:

Router# show route ipv6 191:1::/64 | i multi | utility wc -l
128
Router# show cef ipv6 191:1::/64 | i multipath | utility wc -l
128

Verify the ECMP capabilities of the platform.

Example:

Router# show cef misc
Platform capabilities:

L3 loadbalancing levels: 2 L3 Hash buckets: 64
L3 recursive Hash buckets: 128 L3 Unequal cost hash buckets: 64

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