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I am using PPP to create a IPv6 connection to a remote host.

What is the recommended IPv6 prefix size for a single host at the other end of the PPP connection?

  • Should it be /128, because there is only a single host
  • Should it be /64 to make it more like other setups and allow for the remote host to have multiple IPv6 addresses
  • Something in between?

If /64 does that mean I should be allocating individual /64 allocations for each remote host on its individual PPP connection.

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RFC 6164, Using 127-Bit IPv6 Prefixes on Inter-Router Links explains that /127 networks are good for point-to-point links:

Abstract

On inter-router point-to-point links, it is useful, for security and other reasons, to use 127-bit IPv6 prefixes. Such a practice parallels the use of 31-bit prefixes in IPv4. This document specifies the motivation for, and usages of, 127-bit IPv6 prefix lengths on inter-router point-to-point links.

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  • What if the remote peer is a host, rather than a router?
    – njh
    Feb 21 at 0:16
  • It still works. Unlike the IPv4 /31, which, despite having an RFC, is not supported by everything (Microsoft), everything seems to support IPv6 /127, even Microsoft. There are real reasons that /127 is recommended, including reasons that could affect hosts.
    – Ron Maupin
    Feb 21 at 0:20
  • I believe SLAAC can only be used on subnets with a /64 prefix. Does that mean that /127 subnets must be manually configured? Or can DHCPv6 be used?
    – njh
    Feb 27 at 13:41
  • 1
    Yes, but you always want to statically configure the addressing on your network equipment, e.g. your router. You could use DHCP or static configuration for the host. IPv6 networks smaller than /127 can be vulnerable to ping pong attacks.
    – Ron Maupin
    Mar 22 at 2:33

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