Adam,

To what extent does setting communities on BGP routes work in the real world?

I can't help suspecting that in reality, routes would get aggregated, or communities would be dropped or replaced, somewhere between source and destination.

In order to prepare an IETF draft on the utilization of extended communities to control the redistribution of routes (see http://www.infonet.fundp.ac.be/doc/reports/draft-bonaventure-bgp-redistribut...) we did a study of the utilization of the community attribute for traffic engineering purposes. This study was based on two sources of information : - the RIPE whois database for the advertised communities - the BGP routing tables collected by RIPE and routeviews This analysis shows that BGP communities are becoming frequently used for traffic engineering purposes. A summary of our findings is available as http://www.infonet.fundp.ac.be/doc/tr/Infonet-TR-2002-02.html and you can find the analysed data on the web as well, see http://alpha.infonet.fundp.ac.be/anabgp/ Our intention is submit this analysis as an informational RFC one day to document the common utilizations of the community attribute in today's Internet. Comments on the above mentionned report are welcome. Best regards, Olivier Bonaventure --- http://www.infonet.fundp.ac.be