Because the dominant ISP (Telenet) has enabled IPv6 by default on all their residential gateways. And because they (possibly somewhat surprisingly) have some smart people working for them.
That's remarkable, since Telenet is part of Liberty Global, who owns so many ISP's. Eg. neighbouring country The Netherlands has Ziggo (also owned by Liberty Global). Adaptation in The Netherlands is only 9 pct. Makes me wonder if Belgium is used as a technical testing playground for Liberty Global or if it's just a smart move by Telenet.
Depending on where you are in the Netherlands Ziggo will give proper Dual Stack or DS-lite to new customers. It reflects the networks that Ziggo was cobbled together from. If you are in a former UPC area you probably want to call them and ask them to downgrade you back to IPv4 (they do this for free). Their DS-lite solution employs carrier grade NAT which blows dog chunks.
DS-Lite[0] means you have proper native IPv6 but only a tunnel on top of that for v4, so it's unlikely that IPv6 connections are negatively affected by this setup.
My understanding is that for historical reasons the newer ISPs (mostly cable providers) were running out of IPv4 addresses. They then switched their own networks over to IPv6, meaning that if you live in Belgium, there's a very high chance your router has an external IPv6 address and not an IPv4 one.
Because they were running out of IPv4 addresses and they are legally required to not have more than IIRC 16 customers behind one address at any time for law enforcement reasons, so they figured that CGN wasn't worth it and decided to adopt IPv6 instead.
Not all customers do. Professional contracts and people asking special stuff or modifying their (Telenet-managed) firewall settings automatically get one. Other consumers - which is the large part of their customer base - get IPv6 with CGN/NAT64 with maximum 16 clients NAT'ed behind a public IPv4 address for legal wiretap+privacy reasons.
Really? I've never seen anyone with a shared IPv4. Maybe because every time I look into it the first thing I do is modify their firewall settings slightly. Heh.
ISP's could argue that websites should be logging source port numbers of tcp connections. That would allow them to have thousands of customers behind the same IP, and still able to identify a single one.
BTW, I just noticed: No, you cannot realistically have thousands of customers behind the same IP. There are only 65535 TCP ports per IP address, just loading your typical website that loads resources from tons of domains can easily need a hundred ports at once.
No, they couldn't, because that would be illegal. An ISP cannot just record the communication of their customers because it makes thing cheaper for them.
Also, that easily generates petabytes of logs, so it's not really cheap either.
As an end-customer in Germany, 30.76% is a lie. Most big ISP don't even have any (public) plans to support at least a double-stack. However, as rumours say, internally it's all v6 now. The best you can hope for (providing you have a custom and not supplied router) is 6to4.
