I have tried configuring a Ipv6 subnet address 2001:0dce:0000:0000::1/53 into the router interface.

It works but when the I tried setting the auto-configuration button on the PC connected to this interface, it does not work. However, if I put the Ipv6 address as 2001:0dce:0000:0000::1/64, it works instead. But for my project, it requires a /53 prefix length. How can I fix this?

  • You really only want to use /64 IPv6 networks as other sizes break some IPv6 features. See the answer to this question.
    – Ron Maupin
    Aug 14 at 14:30
  • "Break". I've used non-/64's for many, many years without any broken behavior. (I do so intentionally to stop SLAAC... android won't do anything but SLAAC.)
    – Ricky
    Aug 14 at 14:35
  • Also, the "64bit boundary" is antithetical to the foundation of IPv6: there are no classes, there is no line dividing "host" and "network". But since SLAAC drew that line, every other nut has hitched their horse to it.
    – Ricky
    Aug 14 at 14:45

SLAAC REQUIRES the prefix length be 64. If it is not, DHCPv6 (and static) is the only way hosts can get an address.

  • 1
    For the record, I've crusaded against this stupid, unnecessary limitation for a decade. Since almost everything supports privacy extensions and DAD, there's no reason to keep clinging to the infinitely bad idea of EUI-64 (MAC) derived automatic addresses.
    – Ricky
    Aug 14 at 14:32
  • 1
    I've been on the same side of that "crusade" for a while; my presentation sides on some of the problems with /64 LANs and mitigations (some of which have been implemented by Cisco, Juniper, and others in the years since): inconcepts.biz/~jsw/IPv6_NDP_Exhaustion.pdf Aug 14 at 14:41

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