On Sun, Apr 24, 2005 at 11:26:12AM +0200, Iljitsch van Beijnum wrote:
At the end of the day, it's individual ISPs who decide what they allow and don't allow in their routing tables. It's true that if you announce a smaller block than a /32 you'll be filtered in many places. However, this isn't necessarily a problem. For instance, if someone in Asia sends your customer who has a /48 from you and also announces this /48 to another ISP, and the Asian network filters the / 48, the packet will flow towards Europe as per your /32. Then when it gets to Europe, it's pretty likely that the packet will hit an ISP who actually has the /48 in their routing table. After all, what's allowing a few /48s from the people you get drunk with at all those RIPE meetings?
The filtering out there IS a problem. For an example what happens when you try multihoming with </32, see: http://www.sixxs.net/tools/grh/lg/?prefix=2001:1578::/32 It's not that extreme in this case, as some/many people seem to filter "<=/48" instead of ">/32" and /40s do pass, but in general your AS_PATHs for the more-specifics can get VERY long. So borderline is that you have worse to MUCH worse connectivity by announcing the more-specific than via the aggregate, thanks to the filtering done out there. Regards, Daniel -- CLUE-RIPE -- Jabber: dr@cluenet.de -- dr@IRCnet -- PGP: 0xA85C8AA0