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

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BGP community and extended-community advertisements

Updated: February 28, 2026

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Overview

Explains the use of BGP communities and extended communities to tag routes for policy enforcement and traffic management.

BGP community and extended-community advertisements are mechanisms that

  • specify that community or extended-community attributes should be sent to an eBGP neighbor

  • are not sent to an eBGP neighbor by default, and

  • are always sent to iBGP neighbors by default.

Guidelines for BGP community and extended-community advertisements

  • If you configure the send-community-ebgp command for a neighbor group or address family group, all neighbors using that group inherit the configuration.

  • Configuring the command specifically for a neighbor overrides the inherited values.

  • You cannot configure BGP community and extended-community filtering for iBGP neighbors.

  • BGP always sends communities and extended-communities to internal BGP (iBGP) neighbors under VPNv4, MDT, IPv4, and IPv6 address families.

Configure BGP community and extended-community advertisements

Enable the router to send community or extended-community attributes to an eBGP neighbor.

By default, BGP does not send community or extended-community attributes to an eBGP neighbor. This task provides the procedure to enable this advertisement.

Procedure

1.

Configure the BGP neighbor, specifying its IP address and remote autonomous system number.

Example:

Router# configure
Router(config)# router bgp 120
Router(config-bgp)# neighbor 172.168.40.24
Router(config-bgp-nbr)# remote-as 2002
Router(config-bgp-nbr)# address-family ipv6 unicast
2.

Configure the router to send community attributes or extended community attributes to the specified eBGP neighbor.

  • Router(config-bgp-nbr-af)# send-community-ebgp
Router(config-bgp-nbr-af)# commit
  • Router(config-bgp-nbr-af)# send-extended-community-ebgp
Router(config-bgp-nbr-af)# commit