[casca]

There's always been a vocal group who maintains that the IP addresses that are not visible on the internet should be returned. There are a number of problems with this argument.

Firstly, there are legitimate business reasons for having assigned, non-RFC1918 addresses that are only used internally. Interconnecting private networks belonging to different organizations that have overlapping 10.x addresses is a painful process. Sure it's possible to NAT, but given that the IP addresses are effectively an asset of the organization, why not use them? I'm not implying that this is right, but it's how the system was in the past and the cost of changing internal networking and applications could be very high.

Secondly, how do you prove that an IP address is accessible on the Internet? Many IPs do not respond to pings and I can easily set up a device that will answer for all IPs behind the corporate gateways.

[p1mrx]

> how do you prove that an IP address is accessible on the Internet?

If an address isn't announced in BGP, then for most practical purposes, it's not on The Internet.

But I'm sure that if someone acquired the authority to start reclaiming unannounced /8s, the entities holding them would figure out how to announce them quite quickly.

[nwh]

I'd rather just see the massive corporate reservations returned.

Why does Xerox need an entire A block, why do Apple, BMW?

[ctrl_freak]

> Why does Xerox need an entire A block, why do Apple, BMW?

They don't, but retroactively taking away their /8s would be extremely complicated and expensive for them, not to mention that there is very little benefit from prolonging exhaustion by perhaps 1-2 years at most.

[nwh]

They could buy the ranges back if they really desired. The results from the Carna botnet show just how sparse the usage of the allocated ranges is. It's practically empty for the entire left upper quadrant.

http://internetcensus2012.bitbucket.org/images/hilbert_icmp_...

[wmf]

A lot of IP addresses are used but not visible from the public Internet.

[nwh]

Oh I realise, I just have a hard time believing that Ford even has a tiny portion of their block allocated to anything.

[rjsw]

Ford has multiple design centres in different countries plus a lot of subcontractors who may need to connect to stuff from outside.

I can believe that they are using a large part of an /8.

[kalleboo]

> Interconnecting private networks belonging to different organizations that have overlapping 10.x addresses is a painful process

They could just use IPv6 for that