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

Multi-instance and multi-AS BGP

Updated: February 28, 2026

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Overview

Restrictions and guidelines for multi-instance BGP

Instance limits and identification
Address family configuration
Configuration management
Guidelines

Overview

Describes a configuration approach that uses unique AS numbers per BGP instance, isolates address families, and enables scaling by distributing peer sessions and tables.

Multi-instance and multi-AS BGP is a configuration approach that

allows each BGP instance to use a unique AS number
provides address family isolation by mapping different address families to separate BGP instances, and
enables higher scaling and more granular resource management by distributing peer sessions and BGP tables across instances.

Restrictions and guidelines for multi-instance BGP

This section outlines the restrictions and provides guidelines for configuring and managing multi-instance BGP on a router.

Instance limits and identification

A router supports a maximum of four BGP instances.
Each BGP instance must have a unique router ID.

Address family configuration

Only one address family can be configured under each BGP instance, except VPNv4, VPNv6, and RT-Constrain.
IPv4/IPv6 unicast and their labeled variants must reside in the same BGP instance.
IPv4/IPv6 multicast must reside in the same BGP instance as their unicast counterparts.

Configuration management

All configuration changes for a single instance can be committed together; however, changes for multiple instances must be committed separately.

Guidelines

We recommend using unique update-source interfaces in the default VRF over all instances when peering with the same remote router.

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