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 <[email protected]>
To: [email protected]
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
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