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IPv4 Waste

greg@... 9th Sep 2010

There is so much waste in the IPv4 space to begin with. Many respondents touched on all the unused class A (or B for that matter) space. That's certainly one way to conserve address space.

So many DSL and a few Cable internet providers chose an address space wasting deployment strategy. It ticks me off every time I have to configure a customer. I've even run across small local/regional DSL providers who are doing this.

Even if a customer wants a single static IP, you end up with two IPs because one goes to the cable or DSL modem and one goes to your router. Even if you don't plan on using the CABLE/DSL modem as a router. That's what they provide, and they require you to use theirs.
Sure, it's just a little /30 (For your CIDR people), but that second IP is not usable to you, and of course then you have a Network and a Broadcast address, and essentially you have wasted 3 out of 4 ip's. (Network - Wasted, Cable Modem- Wasted, Usable IP, Broadcast - Wasted)

All of those modems end up talking to a common gateway anyway upstream on the provider network. So why not cut out the middle man and have more common gateways. You're not likely to have much broadcast traffic at that level of the network anyway. Make it a /24 or a smaller supernet, with a common gateway. Then route subnets to them if they need a block of IP's, or they use that single IP if they only need one.

Even if the two large cable companies who operated like this only changed 1 million customers each, that's now 2 million customers. Those 2 million customers have 2 million usable IP's, but waste 6 million (for the most part.. again once you factor in network, broadcast, and the cable modem).
Once you factor the redesigned networks, you will still have broadcast and networks, but you will have 1/3 of the wasted address space. Even if you could reclaim and reuse 4 million of those 6 million wasted addresses. Those providers would have no need to request additional address space for a long time.