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Bill,
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<div class="">Are your sure about your Error #2, where you say "Prefixes from the same AS are not required to have direct connectivity to each other and many do not."? </div>
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<div class="">From BGP definitions:</div>
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<div class=""><i class="">The AS represents a connected group of one or more blocks of IP addresses, called IP prefixes, that have been assigned to that organization and provides a single routing policy to systems outside the AS.</i></div>
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<div class="">“...<i class="">a connected group..."</i> implies that all the prefixes in an AS must have direct connectivity to each other (direct meaning within the IGP of the AS). I realize that some AS’s have hot backup facilities that they advertise with
heavy prefixing, but in my experience, the backup facility must still be interconnected with the rest of the AS, because prefixing doesn’t guarantee no packets will its that border router. </div>
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<div class=""> -mel</div>
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<div class="">On May 30, 2019, at 9:54 AM, William Herrin <<a href="mailto:bill@herrin.us" class="">bill@herrin.us</a>> wrote:</div>
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<div dir="ltr" class="gmail_attr">On Thu, May 30, 2019 at 8:30 AM Robert Blayzor <<a href="mailto:rblayzor.bulk@inoc.net" class="">rblayzor.bulk@inoc.net</a>> wrote:<br class="">
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On 5/24/19 2:22 PM, William Herrin wrote:<br class="">
> Get it? I announce the /24 via both so that you can reach me when there<br class="">
> is a problem with one or the other. If you drop the /24, you break the<br class="">
> Internet when my connection to CenturyLink is inoperable. Good job!<br class="">
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It would be dropped only if the origin-as was the same. Your AS and your<br class="">
carriers aggregate announcement would be from two different origin AS.<br class="">
At least that's the gist of it...<br class="">
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<div class="">Hi Robert,</div>
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<div class="">Error #1: <a href="https://tools.ietf.org/html/rfc6996" class="">https://tools.ietf.org/html/rfc6996</a> section 4.</div>
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<div class="">It's permissible to announce to your transits with a private AS which they remove before passing the announcement to the wider Internet. As a result, the announcement from each provider will have that provider's origin AS when you see it even
though it's actually from a downstream multihomed customer.<br class="">
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<div class="">Error #2: An AS is an informative handle, not a route. In routing research parlance, an identifier not a locator. Prefixes from the same AS are not required to have direct connectivity to each other and many do not. The origin AS could solve this
by disaggregating the announcement and sending no covering route, but that's exactly what you DON'T want them to do.<br class="">
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<div class="">Regards,</div>
<div class="">Bill Herrin</div>
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<div class="">William Herrin</div>
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<div class=""><a href="https://bill.herrin.us/" target="_blank" class="">https://bill.herrin.us/</a><br class="">
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