When obtaining one route during the resolution of the update packet, the BGP first iterates the route.
If route iteration is successful, the route is reachable and valid. Otherwise, the route is invalid.
Then, the route is available for routing. If this route is preferred, the route becomes the best route.

easy note to understand the difference between valid best and valid. thanks

helpful for me also

good note

good

good to know about that

useful document, thanks

useful document, thanks