Hi, On Fri, 15 Oct 2010 12:26:13 -0700 Zaid Ali <z...@zaidali.com> wrote:
> SO I have been turning up v6 with multiple providers now and notice that > some choose /64 for numbering interfaces but one I came across use a /126. A > /126 is awfully large (for interface numbering) and I am curious if there is > some rationale behind using a /126 instead of a /64. > If you're not going to follow the IPv6 Addressing Architecture, which says /64s for everything, then the prefix length decision is pretty much arbitrary - there is nothing that special about /112s, /126s, /127s or /128s (or /120s or /80s) - they all break something in the existing IPv6 RFCs so once you've passed that threshold then you're really only choosing your poison. If you're going to go down that latter path, I'd suggest reserving a /64 for each link, and then using a longer prefix length out of that /64 when you configure the addressing, to make it easier if you decided to change back to /64s at a later time. Regards, Mark.
