i still advertise the aggregate as a backing route. one reason i might like advertising a /24 is (usually) it's a nice way to gently attract return traffic down a certain path so i can do maintenance on the other side. plenty of other ways to do this, i know (prepending, communities, etc).
On Thu, Oct 2, 2014 at 9:17 AM, Peter Persson <[email protected]> wrote: > Just a stupid question. > Why do you announce a /24 of a /22? Why not announce the whole /22 > directly? > > Regards, > Peter > > 2014-10-02 18:03 GMT+02:00 ryanL <[email protected]>: > >> hi. relatively new cogent customer. is what i've stated in my subject line >> kinda standard fare with them? >> >> i've discovered that when i advertise a /24 from inside a larger /22 to >> XO, >> (who peers with cogent), and then pull the /24 some time later, that >> cogent >> holds onto the /24 and then bounces packets around in their network a >> bunch >> of times for upwards of 8-10 minutes until they finally yank it. this >> effectively blackholes traffic to my /24 for anyone that is using a path >> thru cogent. >> >> example: http://ryry.foursquare.com/image/0e0K1K0t0W2M >> >> it's been a bit of a frustrating experience talking to their noc to >> demonstrate it, but i'm able to duplicate it on demand. even pushing >> routes >> using their communities to offload the circuit takes forever to propagate >> even on their own looking-glasses. >> >> thx >> >> ryan >> > >
