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<p>opening the link currently gives me a HTTP 500 error, very
fitting :)<br>
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<div class="moz-cite-prefix">Am 12.06.2021 um 04:42 schrieb Dan
Mahoney:<br>
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cite="mid:11AD8F0F-C961-449F-AAD8-3CEACA46685A@prime.gushi.org">
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I only just now found this thread, so I'm sorry I'm late to the
party, but here, I put it on Medium.
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<div class=""><a
href="https://gushi.medium.com/the-worst-day-ever-at-my-day-job-beff7f4170aa"
class="moz-txt-link-freetext" moz-do-not-send="true">https://gushi.medium.com/the-worst-day-ever-at-my-day-job-beff7f4170aa</a><br
class="">
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<div class="">On Mar 12, 2021, at 10:07 PM, Mark Tinka
<a class="moz-txt-link-rfc2396E" href="mailto:mark@tinka.africa"><mark@tinka.africa></a> wrote:</div>
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<div class=""> <font class="" face="Tahoma">Hardly
famous and not service-affecting in the end, but
figured I'd share an incident from our side that
occurred back in 2018.<br class="">
<br class="">
While commissioning a new node in our Metro-E
network, an IPv6 point-to-point address was
mis-typed. Instead of ending in /126, it ended in
/12. This happened in Johannesburg.<br class="">
<br class="">
We actually came across this by chance while
examining the IGP table of another router located in
Slough, and found an entry for 2c00::/12 floating
around. That definitely looked out of place, as we
never carry parent blocks in our IGP. <br class="">
<br class="">
Running the trace from Slough led us back to this
one Metro-E device in Jo'burg.<br class="">
<br class="">
It took everyone nearly an hour to figure out the
typo, because for all the laser focus we had on the
supposed link of the supposed box that was creating
this problem, we all overlooked the fact that the
/12 configured on the point-to-point link was
actually supposed to have been a /126.<br class="">
<br class="">
The reason this never caused a service problem was
because we do not redistribute our IGP into BGP (not
that anyone should). And even if we did, there are a
ton of filters and BGP communities on all devices to
ensure a route such as that would have never made it
out of our AS. <br class="">
<br class="">
Also, the IGP contains the most specific paths to
every node in our network, so the presence of the
2c00::/12 was mostly cosmetic. It would have never
been used for routing decisions.<br class="">
<br class="">
Mark.<br class="">
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