[c-nsp] Route Aggregation and Deaggregation

[Jennifer Pruett]

Tony,

I thought about that too, but I did not see the logic as the /24 that would
be advertised would be based on the destination IP and potentially could be
any of the 32 /24's at any give point in time.

Again, Thanks!

Jen

On Wed, Jul 18, 2012 at 9:49 PM, Tony <td_miles at yahoo.com> 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
>
>
>