Is it time to abandon bogon prefix filters?

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Mon Aug 25 10:08:03 CDT 2008


On Mon, 25 Aug 2008 09:38:00 EDT, Chris Marlatt said:

> IIRC "bogon" is specific to unallocated space. Whether it be advertised 
> or not should not matter.

Right.  Tell that to everybody who's ever been at the wrong end of a bogon
filter for 69/8, 70/8, 71/8...

I'll go out on a limb and say that if you see a BGP announcement for a prefix
you think is a bogon, it's *more* likely that the space is no longer
unallocated and you didn't get the memo, than it's still unallocated but being
pirated by somebody. (Which raises a question - what % of sites that are doing
bogon filtering but *not* listening to something like Team Cymru's bogon feed?
If it's nearly ubiquitous, it's not a big problem.  But given the number of
places that have problems with bogon filters, only a small percentage seem to
be doing so...)

At the point that you're doing bogon filtering, you have no way to disambiguate
those two cases.  Which is why I said it's a BGP announcement filtering issue.
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