Given my PC or any other, which part of the IPv6 address is allocated by the RIR and which part is allocated by the ISP?

I know a prefix of /64 is commonly used, does that mean the bits before the /64 are assigned by the RIR? Am I wrong in understanding that the bits before the /64 are primarily network allocated?

  • For your business, the longest prefix for a site should be /48, and you can break out 65,536 standard /64 IPv6 networks from that for the site.
    – Ron Maupin
    Jan 17, 2019 at 15:16

1 Answer 1


In the RIPE region a /29 (/32) is given to a RIPE member (LIR, Local Internet Registry) as a default. If a LIR needs larger prefix he can get one but has to justify it. So at least the first 29 Bits are from RIPE.

Other regional registries have other policies, it's best to check their websites. The smallest Prefix you should see in the global routing tables is a /48.

RIPE also published a document recommending IPv6 prefix sizes LIRs should assign to end customers.


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