[c-nsp] Route Aggregation and Deaggregation

[Sascha Pollok]

.. and another /23 IMHO :)

-Sascha

On Thu, 19 Jul 2012, Tony wrote:

> I would hope that IF ($deity forbid) you needed to pull a single /24 out of a /19 then it would be done in
> a way to create the smallest number of resulting prefixes, eg:
> 
> /19 = /20 + /21 + /22 + 2x /24
> 
> Which would result in "only" 4 extra prefixes being announced than a single /19.
> 
> 
> regards,
> Tony.
> 
> __________________________________________________________________________________________________________
>       From: Sascha Pollok <nsp-list at pollok.net>
>       To: Tony <td_miles at yahoo.com>
>       Cc: Jennifer Pruett <jennypruett88 at gmail.com>; "cisco-nsp at puck.nether.net"
>       <cisco-nsp at puck.nether.net>
>       Sent: Thursday, 19 July 2012 4:05 PM
>       Subject: Re: [c-nsp] Route Aggregation and Deaggregation
> 
> 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
> 
> 
> 
>