BGP Advertised Routes and Outbound Policy Application
The show ip bgp neighbor x.x.x.x advertised-routes command displays routes advertised to a BGP neighbor before any outbound policies are applied. This means that changes made by route-maps, such as AS path prepending, will not be visible in the output of this command.
However, if a route is denied by a route-map, it will not appear in the list of advertised routes at all, as it is not being advertised to the neighbor.
To observe the effects of outbound policies on BGP updates, including changes made by route-maps, use the debug ip bgp updates command. This command shows the actual updates being sent to neighbors, reflecting any modifications made by outbound policies.