Hacker News Reader

Comment by craftyguy | Hacker News Reader

Honest question, not trying to incite unrest: Why does IPv6 even matter for private networks? My understanding is the main (only?) benefit of IPv6 is the vastly increased address space, are there that many private networks in existence that exhaust all IPv4 private network IP ranges?

View on HN

Even with private networks, having plenty of address bits makes things a lot easier.

My employer's internal network includes hosts with addresses in the 10.0.0.0/8 private address range. So does my home network. I have to be careful when choosing subnets, or else things will break in weird ways when I connect to my work VPN. With IPv6, I don't have to worry about this because every machine can be assumed to have a globally-unique address, even if that address isn't normally exposed to the outside world. And more importantly, it's easy to look at the address prefix and figure out where to route packets.

Ah, that's actually something I have hit (a lot.. my employer's and home's networks also clash), but I didn't realize IPv6 would solve it until now!

> are there that many private networks in existence that exhaust all IPv4 private network IP ranges?

No, but there are many private networks in existence that use overlapping subsets of the private network ip ranges.

I bet there are. It only takes ~16M residential NAT “routers” to hit 2^32 total addresses. And there are way more than 2^32 things on the Internet.

it's much more simple than that.

While there are 16,777,216 available addresses under 10.0.0.0/8, most organizations will do the reasonable thing of allocating nice regular subnets for each area and use case, so you can easily end up with one org using things like

  10.0.0.0/16 for infra
  10.8.0.0/16 for allocating end user /24s
  10.16.0.0/16 for whatever

and then that org will merge with another who as it turns out did exactly the same thing, and now the internal subnets all overlap. Even though each company may only be using a few thousand addresses, the address space itself overlaps.

Even if you can plan things ahead of time and divided the /8 into 32 /13s or something and give each sub company 500k addresses, you'd still be screwed on a merger.

The right description for most networks in finance isn't really private, but rather semi-public. NYSE's matching engines aren't routable over the public internet, but they'll give access to anybody willing to pay the price. Same goes for any of the hundreds of other exchanges out there. And lots of broker/dealers need to talk to multiple different exchanges, as well as to each other. It would be nice to do all of that communication using one globally unique IP address, rather than with a rats nest of NAT for each gateway.

I’ve seen traceroutes on private network setups that involve a catastrophe of different conflicting uses of 10.whatever addresses. Also, people use NAT on some of these private network for reasons that escape me.

Getting everyone on the same address namespace would be a big simplification.

Reply on news.ycombinator.com