<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">For any router which receives both announcements, longest match always wins over all other BGP tie-breaking criteria.<div class=""><br class=""></div><div class="">This is almost always summarized as “Longest Match always wins” because virtually any engineer recognizes that the</div><div class="">winner is selected only from the available contestants, not from unknown distant contestants not present at the router</div><div class="">in question.</div><div class=""><br class=""></div><div class="">Owen</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Sep 16, 2019, at 11:26 , Töma Gavrichenkov <<a href="mailto:ximaera@gmail.com" class="">ximaera@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="auto" class=""><div class="">Peace,<br class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Sep 16, 2019, 6:06 AM Mark Tinka <<a href="mailto:mark.tinka@seacom.mu" class="">mark.tinka@seacom.mu</a>> wrote:</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Longest match always wins... so provided your /22's are in the global<br class="">
table, traffic will follow the path toward them before the /21 is preferred.<br class=""></blockquote></div></div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">Not always.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">E.g. imagine an ISP who has two connections to the outside world: one through a major ISP and the other through an IX.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">Such an ISP would be quite inclined both financially and technically to import routes just from the IX and set the default to the upstream ISP link. Therefore, an advertisement from the IX would always win no matter the length.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">There are more complicated cases as well.</div><div dir="auto" class=""><br class=""></div><div dir="auto" class="">--</div><div dir="auto" class="">Töma</div><div dir="auto" class=""><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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