> On Feb 21, 2017, at 2:21 PM, Karsten Thomann <karsten_thomann@xxxxxxxxx> wrote: > > Satisfies my desired outcome of the text, but I would like to modify it: > IPv6 unicast routing is based on prefixes of any valid length up to > 128 [BCP198]. When using [SLAAC], [ILNP], or [NPT66] the Interface ID > of unicast addresses is required to be 64 bits long. An exception is for > example [RFC6164] which standardises 127 bit prefixes on point-to-point > links. The RECOMMENDED prefix length is 64 bit, but prefix lengths up to > 128 bit can be possible on explicit configuration. > I’m reminded of when a vendor decided that /31 on ethernet was not a suitable configuration and did not properly disclose in the release notes, causing a subsequent series of outages. I’m therefore cautious about the usage of any normative comment on bit mask length. Nothing quite like your interfaces losing their IP config after upgrade because someone decided to more strictly interpret guidance. - Jared