Outbound route advertisements belonging to the core can result in traffic either looping or being black holed, or at a minimum, using a non-optimized path.
Review the router configuration to verify that there is a filter defined to block route advertisements for prefixes that belong to the IP core. The prefix filter must be referenced outbound on the appropriate BGP neighbor statements. If the router is not configured to reject outbound route advertisements that belong to the IP core, this is a finding.
Configure all eBGP routers to filter outbound route advertisements belonging to the IP core.