[c-nsp] Route Aggregation and Deaggregation

[Sascha Pollok]

Hi Jen,

+1 for Tony. I would just like to make clear: please do NOT deaggregate 
the /19. You can advertise a more-specific /24 to ISP3  OR  advertise
the more-specific /24 to all three ISPs. But please do *not* deaggregate
the /19 into 32x /24.

Good luck
Sascha

On Wed, 18 Jul 2012, Tony wrote:

> Hi Jen,
>
> You can do that. All of your traffic for the /24 will come to you via ISP3 as this is a more specific match than the /19 it is part of. If you drop your link to ISP3, then your /24 traffic will then be received via one of the /19's you advertise to ISP1 & ISP2.
>
> If this is your intention, then go for it. No need to also advertise the /24 to ISP1 & ISP2 unless you want some of the traffic for that /24 to come inbound on those links.
>
>
>
> regards,
> Tony.
>
>
>
>
>> ________________________________
>> From: Jennifer Pruett <jennypruett88 at gmail.com>
>> To: cisco-nsp at puck.nether.net
>> Sent: Thursday, 19 July 2012 3:28 PM
>> Subject: [c-nsp] Route Aggregation and Deaggregation
>>
>> Good day!
>>
>> Question for any BGP guru's; we have a couple of ASR routers as our border
>> routers which are advertising a few /19's. The question is not directly
>> related to the ASR hardware, but the
>> process and best practice of aggregating PI assigned space. If we advertise
>> our /19's via ISP1 and ISP2 and then introduce ISP3 and only advertise a
>> /24 from one
>> of the /19's, do we have to deaggregate the /19 that the /24 was pulled out
>> of to accommodate the /24 that we would advertise via ISP3? What are the
>> ramifications of
>> such actions?
>>
>> Thanks for your time
>> Jen