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Consistent routing policy?


On Mon, Sep 16, 2019, 6:06 AM Mark Tinka <mark.tinka at seacom.mu> wrote:

> Longest match always wins... so provided your /22's are in the global
> table, traffic will follow the path toward them before the /21 is
> preferred.

Not always.

E.g. imagine an ISP who has two connections to the outside world: one
through a major ISP and the other through an IX.

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.

There are more complicated cases as well.


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