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.