[192020] in North American Network Operators' Group
Re: nested prefixes in Internet
daemon@ATHENA.MIT.EDU (Martin T)
Mon Oct 10 02:50:43 2016
X-Original-To: nanog@nanog.org
In-Reply-To: <8737ka4j1q.fsf@mid.deneb.enyo.de>
From: Martin T <m4rtntns@gmail.com>
Date: Mon, 10 Oct 2016 09:50:39 +0300
To: Florian Weimer <fw@deneb.enyo.de>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
Florian:
as I told in my initial e-mail, ISP-B is multi-homed, i.e connected to
ISP-A(who leases the /24 to ISP-B from their /19 block) and also to
ISP-C. ISP-B wants to announce this /24 both to ISP-A and ISP-C.
That's the reason why either solution 1 or 2 in my initial e-mail is
needed.
However, I would like to hear from Roy and Mel why do they prefer a
third option where ISP A announces the /19 and the /24 while ISP B
does just the /24.
thanks,
Martin
On Wed, Oct 5, 2016 at 11:50 PM, Florian Weimer <fw@deneb.enyo.de> wrote:
> * Martin T.:
>
>> Florian:
>>
>>> Are the autonomous systems for the /19 and /24 connected directly?
>>
>> Yes they are.
>
> Then deaggregation really isn't necessary at all.
>
>>> (1) can be better from B's perspective because it prevents certain
>>> routing table optimizations (due to the lack of the covering prefix)
>>
>> What kind of routing table optimizations are possible if covering /19
>> prefix is also present in global routing table?
>
> The /24 prefix could arguably be dropped and ignored for routing
> decisions.
