----- Forwarded message from Owen DeLong <owen@delong.com> ----- From: Owen DeLong <owen@delong.com> Date: Tue, 25 Sep 2012 02:02:09 -0700 To: Jeff Wheeler <jsw@inconcepts.biz> Cc: "nanog@nanog.org" <nanog@nanog.org> Subject: Re: IPv6 Address allocation best practises for sites. X-Mailer: Apple Mail (2.1486) On Sep 24, 2012, at 21:08 , Jeff Wheeler <jsw@inconcepts.biz> wrote: > On Mon, Sep 24, 2012 at 6:52 PM, John Mitchell <mitch@illuminati.org> wrote: >> Does the best practise switch to now using one IPv6 per site, or still the >> same one IPv6 for multi-sites? > > Certainly it would be nice to have IPv6 address per vhost. In many > cases, this will be practical. > > It also sometimes will NOT be practical. > > Imagine that I am one of the rather clueless hosting companies who are > handing out /64 networks to any customer who asks for one, and using > NDP to find the machine using each address in the /64. Churn problems > aside, if you have any customer doing particularly dense virtual > hosting, say a few thousand IPv6 addresses on his one or more > machines, then he will use up the whole NDP table for just himself. > You probably won't want to be a customer on the same layer-3 device as > that guy. Now that there might be dozens of VMs per physical server > and maybe 40 physical servers per each top-of-rack device, you can > quickly exhaust all of your NDP entries even with normal, legitimate > uses like www virtual hosting. > That's not the best way to stand up /64s for vhosts. If you're smart, the customer gets a /64 for machine addresses (put your interfaces in this /64) and each machine gets a /64 for vHosts (put your vhost addresses on the loopback interface of the applicable machine). Then, you route the /64 to the machine address for the applicable machine and the vhosts never hit your neighbor table. [snip] Deleted a whole bunch of additional reasons you really want to do things the way I suggest above [/snip] Owen ----- End forwarded message ----- -- Eugen* Leitl <a href="leitlhttp://leitl.org">leitl</a> http://leitl.org ______________________________________________________________ ICBM: 48.07100, 11.36820 http://www.ativel.com http://postbiota.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE