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

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BGP permanent networks

Updated: February 28, 2026

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Overview

Describes BGP permanent network functionality, outlining operational restrictions and providing procedures to configure and advertise permanent networks within BGP environments.

A BGP permanent network is a Border Gateway Protocol (BGP) feature that

  • enables the creation and advertisement of selected prefixes (IPv4 or IPv6) using route-policies

  • ensures these routes remain in the routing table until explicitly removed by an administrator, and

  • allows the configuration and selective advertising of permanent paths to designated BGP peers.

Permanent path behavior

For each designated prefix, BGP establishes a permanent path. The permanent path is considered less preferred than dynamic BGP paths learned from peers and is only downloaded into the Routing Information Base (RIB) if it is evaluated as the best path. Permanent paths are selectively advertised and persist independently of changing network conditions.

Restrictions on BGP permanent networks

Review these restrictions before you configure BGP permanent networks:

  • Use this feature only with IPv4 unicast and IPv6 unicast address families within the default Virtual Routing and Forwarding (VRF) context.

  • Ensure that permanent paths are selectively advertised and persist only as described. Permanent paths do not override dynamic BGP paths unless you select them as the best path.

Configure a BGP permanent network

Configure a BGP permanent network to ensure designated prefixes are always advertised.

Use this task when you need certain prefixes to remain permanently available in BGP advertisements, regardless of current route availability.

Before you begin

  • Ensure you have identified the IPv4 or IPv6 prefixes that should always be advertised.

Follow these steps to configure a BGP permanent network.

Procedure

1.

Define a prefix set for permanent network prefixes.

Example:


Router(config)# prefix-set PERMANENT-NETWORK-IPv4
Router(config-pfx)# 10.1.1.1/32,
Router(config-pfx)# 10.2.2.2/32,
Router(config-pfx)# 10.3.3.3/32
Router(config-pfx)# end-set
2.

Create a route policy to match the prefix set.

Example:


Router(config)# route-policy POLICY-PERMANENT-NETWORK-IPv4
Router(config-rpl)# if destination in PERMANENT-NETWORK-IPv4 then
Router(config-rpl)# pass
Router(config-rpl)# endif
3.

Enter BGP configuration mode, and configure the permanent network using the route-policy you created.

Example:

Router(config)# router bgp 100
Router(config-bgp)# address-family ipv4 unicast
Router(config-bgp-af)# permanent-network route-policy POLICY-PERMANENT-NETWORK-IPv4
4.

Use the show bgp { ipv4 | ipv6 } unicast command to confirm that the specified prefixes are advertised as permanent networks.

Before you begin

  • Identify the autonomous system numbers and the IP addresses of the BGP peers you want to configure.

Follow these steps to advertise a permanent network to BGP peers.

Procedure

1.

Enter BGP configuration mode, specify the neighbor IP address, and enable permanent network advertisement for that neighbor.

Example:

Router# configure
Router(config)# Router(config-bgp)# neighbor 10.255.255.254
Router(config-bgp-nbr)# remote-as 4713
Router(config-bgp-nbr)# address-family ipv4 unicast
Router(config-bgp-nbr-af)# advertise permanent-network
2.

Use the show bgp {ipv4 | ipv6} unicast neighbor ip-address command to to verify if permanent network advertisement is enabled.