cogent update suppression, and routing loops

Thu Oct 2 16:44:26 UTC 2014

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 <peter.persson at bredband2.se>
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 <ryan.landry at gmail.com>:
>
>> 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
>>
>
>