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MediaWiki's explanation of IPv6 range blocks is not great, so I have created a guide for people who do not speak MediaWiki developer on how to deal with disruption from IPv6 ranges.
If you want to know the technical stuff, you can read mw:Help:Range blocks/IPv6 or IPv6. The basics are this: each connection that uses IPv6 has access to many IP addresses on a range, and for many users the individual IPv6 address can change frequently, sometimes even within an hour. The net effect of this is that blocks of individual IPv6 addresses can quickly stop being effective.
While IPv6 ranges can get very large and have many users, typically one user/connection/physical location has access to a /64 range, and you can usually treat this as you would one IPv4 address. For all IP address ranges, the smaller the number after the / the larger it is. In IPv6, this gets very large very fast. As an example, an IPv6 /60 is significantly larger than a /64.
How to block most IPv6s you come across
- Click on the individual IP address to bring up the contributions
- Type /64 on the end of the IP in the contributions box to bring up all the contributions for the range. You can generally assume this is one person/one physical location.
- Click block and treat it like you would one individual IP address.
Some providers such as Verizon Wireless have their customers float along much larger ranges. Blocking the /64 will not completely stop disruption from these ISPs, but it also won't really cause much collateral damage either. If you are uncomfortable with how IPv6 works, you should not block ranges wider than the /64 because they get really wide really fast, but even if you aren't that technically minded, don't worry about blocking the /64. Just block it. Odds are, the people using it are who you want to block.
As always there are exceptions. Some individual IPv6 addresses belonging to mobile networks are shared, so always check the contributions. As an example, a /64 from AT&T Wireless in some regions will be shared by many users. A look at the volume of contributions will usually be enough to detect this. If something looks like it belongs to multiple people, and you are not familiar with the ISP, you can always ask someone else for help. CheckUsers are normally familiar with various ISPs and range blocks, and can typically give you advice.