was bogon filters, now "Brief Segue on 1918"

Darden, Patrick S. darden at armc.org
Wed Aug 6 08:25:36 CDT 2008

Was looking over 1918 again, and for the record I have only run into one
network that follows:

   "If two (or more) organizations follow the address allocation
   specified in this document and then later wish to establish IP
   connectivity with each other, then there is a risk that address
   uniqueness would be violated.  To minimize the risk it is strongly
   recommended that an organization using private IP addresses choose
   *randomly* from the reserved pool of private addresses, when
   sub-blocks for its internal allocation."

I added the asterisks.

Most private networks start at the bottom and work up: 192.168.0.X++,
10.0.0.X++, etc.  This makes
any internetworking (ptp, vpn, etc.) ridiculously difficult.  I've seen
a lot of hack jobs
using NAT to get around this.  Ugly.

--Patrick Darden

-----Original Message-----
From: Darden, Patrick S. 
Sent: Wednesday, August 06, 2008 9:19 AM
To: 'Leo Bicknell'; nanog at nanog.org
Subject: RE: Is it time to abandon bogon prefix filters?

Yes.  1918 (10/8, 172.16/12, 192.168/16), D, E, reflective (outgoing
mirroring), and as always individual discretion.

--Patrick Darden

-----Original Message-----
From: Leo Bicknell [mailto:bicknell at ufp.org]
Sent: Wednesday, August 06, 2008 9:10 AM
To: nanog at nanog.org
Subject: Is it time to abandon bogon prefix filters?

"Bogon" filters made a lot of sense when most of the Internet was
bogons.  Back when 5% of the IP space was allocated blocking the
other 95% was an extremely useful endevour.  However, by the same
logic as we get to 80-90% used, blocking the 20-10% unused is
reaching diminishing returns; and at the same time the rate in which
new blocks are allocated continues to increase causing more and
more frequent updates.

Have bogon filters outlived their use?  Is it time to recommend people
go to a simpler bogon filter (e.g. no 1918, Class D, Class E) that
doesn't need to be updated as frequently?

       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/

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