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

BGP multipath next-hop and as-path control

Updated: February 28, 2026

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Overview

Guidelines for BGP multipath next-hop and as-path control
Topology illustrating routing loop formation

Overview

Describes enhancements that prevent next-hop overwriting and allow control over as-path usage in multipath route selection to maintain predictable and loop-free routing.

BGP multipath next-hop and as-path control is a set of enhancements that:

prevents overwriting of next-hop values for multipath prefixes,
allows you to control how as-path information is used when selecting multipath routes, and
helps maintain predictable and loop-free routing behavior.

You can use the next-hop-unchanged multipath command to ensure that BGP does not recalculate the next hop for multipath prefixes.

The bgp multipath as-path ignore onwards command enables you to ignore as-path attributes beyond a certain point when computing multipath, allowing for more flexible path selection.

Guidelines for BGP multipath next-hop and as-path control

Use the next-hop-unchanged multipath command to disable next-hop recalculation for multipath prefixes and preserve the original next-hop values.

Caution

Use the bgp multipath as-path ignore onwards command with caution. If you enable this command on multiple interconnected routers, it may cause routing loops.

Topology illustrating routing loop formation

Illustrate how specific BGP multipath configurations can create routing loops between connected routers.

Figure 1. Topology example: routing loop formation

Consider three routers named R1 in AS-1, R2 in AS-2, and R3 in AS-3, with each router in a different autonomous system and all interconnected. R1 announces a prefix to both R2 and R3. If R2 and R3 are both configured for multipath and have the bgp multipath as-path ignore onwards command enabled, each router may forward part of its traffic to the other. This behavior creates a forwarding loop between R2 and R3. To avoid such loops, do not enable the as-path ignore onwards option on interconnected routers.

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