On Jan 5, 2011, at 7:04 AM, Jack Bates wrote: > On 1/5/2011 6:29 AM, Dobbins, Roland wrote: >> >> Using /64s is insane because a) it's unnecessarily wasteful (no >> lectures on how large the space is, I know, and reject that argument >> out of hand) and b) it turns the routers/switches into sinkholes. >> > > Except someone was kind enough to develop a protocol that requires /64 to > work. So then there is the SLAAC question. When might it be used? > > With routers, I usually don't use SLAAC. The exception is end user networks, > which makes using SLAAC + DHCPv6-PD extremely dangerous for my edge routers. > DHCPv6 IA_TA + DHCPv6-PD would be more sane, predictable, and filterable (and > support longer than /64) thought my current edge layout can't support this > (darn legacy IOS). > > I would love a dynamic renumbering scheme for routers, but until all routing > protocols (especially iBGP) support shifting from one prefix to the next > without a problem, it's a lost cause and manual renumbering is still > required. Things like abstracting the router id from the transport protocol > would be nice. I could be wrong, but I think ISIS is about it for protocols > that won't complain. > > All that said, routers should be /126 or similar for links, with special > circumstances and layouts for customer edge. > Why shouldn't I use /64 for links if I want to? I can see why you can say you want /126s, and that's fine, as long as you are willing to deal with the fall-out, your network, your problem, but, why tell me that my RFC-compliant network is somehow wrong?
> For server subnets, I actually prefer leaving it /64 and using SLAAC with > token assignments. This is easily mitigated with ACLs to filter any packets > that don't fall within the range I generally use for the tokens, with > localized exceptions for non-token devices which haven't been fully > initialized yet (ie, stay behind stateful firewall until I've changed my IP > to prefix::0-2FF). I haven't tried it, but I highly suspect it would fail, > but it would be nice to use SLAAC with longer than /64. > SLAAC cannot function with longer than /64 because SLAAC depends on prefix + EUI-64 = address. Owen
