From: Bruce Robertson <bruce@greatbasin.net>
...
Currently, one half of our /18 is being erroneously advertised by
Sprint (207.228.0.0/19). This, naturally, is causing us no end of
trouble. Sprint, meanwhile, blames a third party. This has been
going on for over 24 hours.
You have to make certain that your upstream provider(s) will accept all more
specific routes from you for networks in your CIDR block. That way as soon
as you notice a problem such as the one above for example, you could announce
207.228.0.0/20 and 207.228.16.0/20 to the world. Since you are announcing
more specific routes you have immediately fixed your routing problem.
THEN you beat up on the offender and offender's NSP to fix their announcement.