IPv6 /64 links (was Re: ipv6 book recommendations?)

Wed Jun 6 14:35:48 UTC 2012

Anton Smith <anton at huge.geek.nz> a écrit sur 06/06/2012 09:53:02 AM :

> Potentially silly question but, as Bill points out a LAN always 
> occupies a /64.
> 
> Does this imply that we would have large L2 segments with a large
> number of hosts on them? What about the age old discussion about
> keeping broadcast segments small?

The /64 only removes the limitation on the number of *addresses* on 
the L2 domain. Limitations still apply for the amount of ARP and 
ND noise. A maximum number of hosts is reached when that noise
floor represents a significant portion of the link bandwidth. If
ARP/ND proxying is used, the limiting factor may instead be the 
CPU on the gateway. 

The ND noise generated is arguably higher than ARP because of DAD, 
but I don't remember seeing actual numbers on this (anybody?). 
I've seen links with up to 15k devices where ARP represented 
a significant part of the link usage, but most weren't (yet) IPv6. 

/JF