Re: [Lsr] Prefix Unreachable Announcement Use Cases

Robert Raszuk <> Mon, 16 November 2020 08:25 UTC

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From: Robert Raszuk <>
Date: Mon, 16 Nov 2020 09:25:24 +0100
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To: Aijun Wang <>
Cc: Jeff Tantsura <>, lsr <>, "Acee Lindem (acee)" <>
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Subject: Re: [Lsr] Prefix Unreachable Announcement Use Cases
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> I was not bringing RIFT's negative routies example as something inherently
> negative. I was just pointing it out to illustrate that today's data plane
> lookup does not really support "if does not match" checks.
> *[WAJ] In data plane, the device do still the “match” check, not “does not
> match” check.  When the router receives the PUA information, it will
> install one black hole route for a short time.*

So your idea is that you install route for unreachable prefix to /dev/null

And how would that help connectivity restoration ?

Moreover it seems that it will just also prevent any local protection to
locally bypass the failed destination.

Bottom line is that I agree with one problem statement. However IMHO
described actions upon reception of PUA are questionable at best.