Hello Jennifer
If you make a change to a routing policy (policy attributes or filters) then in order to make those policies take effect you must apply one of the three solutions stated in the lesson. If you do not, these policies will never be applied.
Note that the changing of the policies is different than the updating of prefixes. Prefixes are exchanged between BGP routers, and when changes do take affect, based on the BGP timer, BGP will converge. Specifically, BGP uses a keepalive message sent every 60 seconds, and a holdtime timer of 180 seconds. Additionally, uses a scanner that checks all routes in the BGP table every 60 seconds. These mechanisms are used for sharing prefixes and routing convergence.
However, for attribute changes, that is, changes to the way that the router will interpret and handle BGP information received, these won’t take effect unless one of the three methods in the lesson are employed.
I hope this has been helpful!
Laz