I am studying BGP communities at the moment.
I understand that communities are path attributes which are a way of tagging specific BGP route advertisements in order to ensure proper route selection policies/traffic engineering, etc.
I've seen examples of BGP communities like this that ISPs and their customers can use, for example, here's some from an ISP in the US
So if I understand this correctly, if a customer tags their prefixes with 64983:0, for example, then the ISP will prepend the AS number 3 times to all their BGP neighbors. If the customer tags their prefixes with 3356:90, then they will set the LOCAL_PREF to 90.
I understand how these communities work but the question is, when exactly would I want to use them in the real world? Couldn't all this traffic engineering and route selection be simply achieved by having the customer configure a route-map and set the LOCAL_PREF, MED, AS Path Prepending and the rest for their prefixes there? If so, why use a community?
If the customer wants to prepend its AS 3 times, they could just configure a route-map and configure it there instead of tagging their routes with a community.
Does anyone please have an example of where a community would be more suitable than what I've mentioned above?
Thank you in advance for your help.