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

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BGP multi-instance and multi-AS support

Updated: February 28, 2026

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Overview

Describes support for BGP multi-instance and multi-AS configurations, explaining requirements and providing tasks for configuring multiple BGP instances for specific autonomous systems.

BGP multi-instance and multi-AS are mechanisms that

  • combine services from multiple routers into a single IOS XR router

  • achieve address family (AF) isolation by configuring different address families in separate BGP instances, and

  • increase session scale by distributing peering sessions across multiple BGP instances.

This feature enables each BGP instance on a router to operate with a unique Autonomous System (AS) number. This provides enhanced flexibility and scalability for complex network environments.

Benefits of BGP multi-instance and multi-AS

These are the benefits of the BGP multi-instance and multi-AS feature:

  • Simplified network management: You can consolidate services from multiple routers into a single IOS XR router. This reduces overall complexity and decreases the effort needed to manage the network.

  • Enhanced control and isolation: By isolating different address families (AFs) in separate BGP instances, you gain better traffic management and policy enforcement.

  • Scalability for large networks: By distributing the load across multiple BGP instances, this feature supports a higher number of peering sessions and larger prefix tables.

  • Improved network stability: By providing faster and more reliable BGP convergence in certain scenarios, this feature increases your network uptime and responsiveness.

  • High availability: With full support for BGP features, including Nonstop Routing (NSR), your network runs continuously and remains resilient.

Requirements for configuring BGP multi-instance and multi-AS

Follow these requirements when configuring BGP multi-instance and multi-autonomous system (multi-AS) features:

Instance limits and identification

  • Limit the router to a maximum of 4 BGP instances.

  • Assign a unique router ID to each BGP instance.

Address family configuration

  • Configure only one address family under each BGP instance. VPNv4, VPNv6, and RT-Constrain address families can be configured under multiple BGP instances.

  • Place IPv4 or IPv6 unicast within the same BGP instance where you configure IPv4 or IPv6 labeled-unicast.

  • Place IPv4 or IPv6 multicast within the same BGP instance where you configure IPv4 or IPv6 unicast.

Configuration management

  • Commit all configuration changes for one BGP instance at the same time.

  • Commit configuration changes for only one BGP instance at a time.

Operational recommendations

Use a unique BGP update-source in the default VRF for each BGP instance when you peer with the same remote router.

Multi-instance BGP support limitation

Multi-Instance BGP is supported only for the Route Reflector (RR) role with EVPN and VPLS-VPWS SAFIs; it is not supported for PE/LER roles.

Configure multiple BGP instances for a specific autonomous system

Configure several BGP instances within a single autonomous system, assigning a unique router ID to each instance.

Before you begin

  • Ensure you have administrative access to the router.

  • Collect autonomous system (AS) numbers and router ID values you want to use.

Follow these steps to configure multiple BGP instances in a specific autonomous system:

Procedure

1.

Enter BGP instance configuration mode for the specific autonomous system and specify a unique name for each instance. Assign a unique router ID value to the BGP instance.

Example:

Router# configure
Router(config)# router bgp 100 instance inst1
Router(config-bgp)# bgp router-id 10.0.0.0
Router(config-bgp)# commit

Ensure that the router ID you assign is unique for each BGP instance in the autonomous system.

Commit all configuration changes for each BGP instance separately. You cannot commit changes for multiple instances at the same time.
2.

Repeat step 1 for each additional BGP instance you want to configure within the same autonomous system, specifying a unique instance name and router ID each time.
Each BGP instance in the specified autonomous system has a unique router ID and its configuration is committed individually.