was bogon filters, now "Brief Segue on 1918"

TJ trejrco at gmail.com
Tue Aug 12 20:57:33 CDT 2008

Michael - good points all, and saved me typing out a reply.

Additionally, using up the RFC1918 space isn't the only problem ... the
previously mentioned collision problems between so-called private networks
become more and more likely (until almost guaranteed).

Only nit:
	"In any case, IPv4 is yesterday's news. Nowadays everyone is
scrambling to integrate IPv6 into their networks and shift services onto
... I would say they should be doing so; I wish more were!!


>-----Original Message-----
>From: michael.dillon at bt.com [mailto:michael.dillon at bt.com]
>Sent: Thursday, August 07, 2008 1:06 PM
>To: nanog at nanog.org
>Subject: RE: was bogon filters, now "Brief Segue on 1918"
>>Your point seemed to be that
>> it is not a large enough allocation of IPs for an  international
>>enterprise of 80K souls.  My rebuttal is: 16.5  million IPs isn't
>You don't seem to understand how IPv4 networks are designed and how that
>interacts with scale, i.e. the large sprawling networks that international
>enterprises have. You don't simply count out x addresses per employee.
>Instead, you design a subnet architecture that a) can grow at all levels,
>and b) can be cut off the network when you sell off a branch operation or
>This leads to large amounts of IP addresses used up in padding at all
>levels, which then leads to these organizations running out of RFC 1918
>space, a more and more common occurence. This, in itself, is a good
>incentive to move to IPv6, since the seemingly wasteful subnet architecture
>is considered best practice with IPv6, and a ULA prefix or two gives you
>lots of space to keep growing.
>>  What are we talking
>> about then?  100 IPs per person--say each person has 10 PCs, 10
>> printers, 10 automated factory machines, 10 lab instruments, 49
>> servers and the soda machine on their network?
>Nope. We are not talking about people, but about network architecture and
>topology. Two people in one office need two addresses. Put them in separate
>offices and they need two subnets. Topology dominates the design.
>> I don't think you have that many soda machines.  Even on 5 continents.
>> Even with your growing Asian market, your suppliers, and the whole
>> marketing team.
>I believe the first two companies to run out of RFC 1918 space (or to
>project that it would happen) are Comcast, and American cable provider in
>one continent, and a Japanese cable provider on a small Pacific island next
>to China.
>> //Err.  Doing it wrong does not justify doing it wrong.
>Cute sound bites does not make you an expert in anything.
>In any case, IPv4 is yesterday's news. Nowadays everyone is scrambling to
>integrate IPv6 into their networks and shift services onto IPv6.
>--Michael Dillon

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