I'm sitting here in the office on a Friday performing some IP maintenance and I see that one of our upstreams is still filtering an IP range we haven't used in years. I dig into it a bit more and it turns out a major carrier still has them SWIPed to us. This got me curious and I dug more into IPs from back in our early days and discovered there are two Tier-1 carriers we no longer do business with that still have large blocks of their own IPs SWIPED and allocated to us. This is really confusing and concerning. I know it's not the end-all-be-all, but I wonder how much IPv4 exhaustion is being caused by this type of IPv4 mis-management, where IPs are still shown as "allocated" to a customer who hasn't used them in years. I've seen this behavior from Frontier and CenturyLink to name just a few. Any thoughts on this?