RFC 7084, "Basic Requirements for IPv6 Customer Edge Routers", November 2013

Note: This RFC has been updated by RFC 9096

Errata ID: 7699
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Alin Nastac
Date Reported: 2023-11-14

Section 4.3 says:

   L-3:   An IPv6 CE router MUST advertise itself as a router for the
          delegated prefix(es) (and ULA prefix if configured to provide
          ULA addressing) using the "Route Information Option" specified
          in Section 2.3 of [RFC4191].  This advertisement is
          independent of having or not having IPv6 connectivity on the
          WAN interface.

It should say:

   L-3:   An IPv6 CE router MUST advertise itself as a router for the
          delegated prefix(es) (and ULA prefix if configured to provide
          ULA addressing) using the "Route Information Option" specified
          in Section 2.3 of [RFC4191], but only when correspondent "Prefix 
          Information Option" is not using the entire prefix delegation or
          its on-link flag is unset. This advertisement is independent of
          having or not having IPv6 connectivity on the WAN interface.

Notes:

When both on-link "Prefix Information Option" and "Route Information Option" will contain the same prefix, hosts that receive such Router Advertisements will have to add 2 almost identical routes in their routing tables:
- PIO route set to "PD/64 dev <incoming_interface>"
- RIO route set to "PD/64 dev <incoming_interface> nexthop <router_ll_address>"

In best case scenario, PIO will take precedence and RIO will have no effect.

In worst case scenario, RIO will take precedence and PIO route will have no effect, which will be equivalent with host ignoring the on-link flag of the PIO.

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