On Tue, Jan 25, 2011 at 9:44 AM, Lasse Jarlskov <laja@telenor.dk> wrote:
Thank you all for your comments - it appears that there is no consensus on how this should be done.
The best piece of advice I received when asking similar questions in the past is to allocate a /64 for every network regardless of it's potential size. Loopbacks, point-to-point, hosting VLANs etc. Then assign whatever size you are currently comfortable with. We've used /128s for loopbacks, safe in the knowledge that we can expand them all to /64s without renumbering (in case someone comes up with a good idea why /64s on loopbacks are necessary.) We've gone unnumbered on point-to-points, as a way of deferring that particular decision. Admittedly this reduces useful diagnostics available from traceroutes, although I quite like seeing loopbacks in traceroutes anyway. Unnumbered does reduce control-plane address space surface, which might be seen as a useful benefit (I'm sure someone will tell me why that's a bad idea.) My point is, if you do your number plan right, you should have some flexibility to make changes in the future without pain. -- Tim:>