From: Jessica Yu <jyy@merit.edu> Subject: Re: CIDR If 131.108 is really critical to my user, I will hate to have my user loose connectivity and yell at me. I'd do some work to anticipate the proble if there is any. I will do a traceroute to see what ASs my traffic to 131.10 traverses and find out the potential CIDR blackhole. Knowing 131.108 will be pulled out proir to its happening does give me advantage. But how can you tell if it's going to work before you pull it out? If some place who doesn't default and isn't on bgpd (too many of them, sigh) then you lose and you don't know that you've lost. What I'm trying to say is that unless you can poke a hole in the cidr block by yanking at least one natural net first, there is no way to debug this other than to rely on everyone giving you a yes/no answer on each CIDR route you advertize. While that would be nice, it doesn't scale past the first few test nets, which was my entire point. The first few times, it's a novelty and you'll get people to tell you if everything is OK, after that, unless you can sniff their BGP tables yourself, it's just a waste of three days.