Re: Large ISPs doing NAT?

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of unadministered, always-on boxes that aren't supposed to be running inbound services in unrouted space would save all of us headaches.

That's almost a better justification for NAT than address-space conservation. ;)

Almost? I'd say it's hands down an EXCELLENT reason. In some configs though, the NAT'd people can still see each other and cause problems, but it still cuts down the exposure.