How does IPv6 subnetting work and how does it differ from IPv4 subnetting?

Posted by Michael Hampton on Server Fault See other posts from Server Fault or by Michael Hampton
Published on 2012-09-11T00:57:56Z Indexed on 2012/09/11 3:40 UTC
Read the original article Hit count: 477

Filed under:

networking

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IPv6

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subnet

This is a Canonical Question about IPv6 Subnetting.

Related:

How does IPv4 Subnetting Work?

I know a lot about IPv4 Subnetting, and as I prepare to (deploy|work on) an IPv6 network I need to know how much of this knowledge is transferable and what I still need to learn. IPv6 seems at first glance to be much more complex than IPv4. So I would like to know:

IPv6 is 128 bits, so why is /64 the smallest recommended subnet for hosts? Related to this:
- Why is it recommended to use /127 for point to point links between routers, and why was it recommended against in the past? Should I change existing router links to use /127?
- Why would virtual machines be provisioned with subnets smaller than /64?
- Are there other situations in which I would use a subnet smaller than /64?
Can I map directly from IPv4 subnets to IPv6 subnets?
My interfaces have several IPv6 addresses. Must the subnet be the same for all of them?
Why do I sometimes see a % rather than a / in an IPv6 address and what does it mean?
Am I wasting too many subnets? Aren't we just going to run out again?
In what other major ways is IPv6 subnetting different from IPv4 subnetting?

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