Choose a two-router link and a two-address prefix
01IPv6 means Internet Protocol version 6. Its addresses have 128 bits. A /127 fixes 127 bits and leaves one bit, giving two addresses for a deliberately configured point-to-point router link.
Separate comparison: adding a host makes a mixed link outside this document’s scope. Link-local addresses are also excluded; this picture does not prescribe changes to them.
Source for this drawing: RFC 6164 · Read RFC section 2 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
This document covers operators assigning specific addresses to point-to-point links with only two routers and no hosts. Ethernet can be configured this way; an ordinary shared LAN is not automatically in scope.
- This document covers operators assigning specific addresses to point-to-point links with only two routers and no hosts. Ethernet can be configured this way; an ordinary shared LAN is not automatically in scope.
- The recommendations do not apply to link-local address scope, router-to-host links, or mixed router-and-host links. This is not a general replacement for host-link /64 or automatic address-configuration rules.
- Routers MUST support assigning /127 prefixes in this scope (§6). That is not a MUST to deploy /127 on every IPv6 link. The example 2001:db8:1::2/127 contains ::2 and ::3; the schematic bit boxes are not width-scaled.
Fictional documentation addresses within 2001:db8::/32. Bounded operator-chosen address examples, not a complete router, Neighbor Discovery, ICMPv6 or address-validation implementation.
Read the RFC section ↗