3

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.

Improve this question
3
  • Did any answer help you? if so, you should accept the answer so that the question does not keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
    – Ron Maupin ♦
    Commented Dec 23, 2021 at 16:53
  • Not really, no. I got an answer about router->router links, when I asked about router->host links. Still hoping there is an RFC somewhere that advises on this.
    – njh
    Commented Jan 5, 2022 at 9:40
  • Do you understand that on a network, a router is a host. A router is simply a host that knows how to reach other networks? Also, other hosts, e.g. PCs, have routing tables and can even forward packets between networks. What distinction are you drawing? The ping-pong attack is mitigated by using /127 links between two devices, and we use that for all point-to-point links.
    – Ron Maupin ♦
    Commented Jan 5, 2022 at 13:23

1 Answer 1

Reset to default
4

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.

Improve this answer
4
  • What if the remote peer is a host, rather than a router?
    – njh
    Commented Feb 21, 2021 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 ♦
    Commented Feb 21, 2021 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
    Commented Feb 27, 2021 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 ♦
    Commented Mar 22, 2021 at 2:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.