Staff

Technical Tip: Removing Remote Peer IP from BGP Advertisement

Forum|Forum|4 months ago
April 10, 2026
0 replies
424 views

Description

This article describes the process of identifying and removing a remote peer IP from BGP advertisement. The user is experiencing an issue where the public IP of the data center firewall is being advertised via ExpressRoute through BGP, and needs to remove this subnet from the BGP advertisement.

Scope

FortiGate, FortiManager.

Solution

To remove the remote peer IP from the BGP advertisement, follow these steps:

Run the command get router info bgp network to list all networks being advertised by the FortiGate
Run the command get router info bgp neighbors <neighbor-IP> advertised-routes to list the routes being advertised to specific BGP peers
Run the command get router info routing-table all to check the routing table.
Check if there are any route maps or prefix lists applied that might be advertising the public IP. If a route map or prefix list is causing the advertisement, modify it to exclude the public IP.
Refer to the Fortinet Community for more information on controlling BGP route advertisement with prefix lists.

The BGP debugging will share that the outgoing prefix list is being applied:

diagnose debug rese

diagnose ip router bgp all enable
diagnose ip router bgp level info
diagnose debug enable

To stop the debugging:

diagnose debug disable
diagnose ip router bgp all disable
diagnose ip router bgp level none