IPv6 Subscriber Access Deployments

Tue Sep 8 20:13:55 UTC 2015

If you can't hang 4k customers off a switch, why does IPv6 need so many bits for the host portion?

Matthew Kaufman

(Sent from my iPhone)

> On Sep 8, 2015, at 12:54 PM, Valdis.Kletnieks at vt.edu wrote:
> 
> On Tue, 08 Sep 2015 19:40:44 -0000, Josh Moore said:
> 
>> The question becomes manageability. Unique VLAN per customer is not always
>> scalable. For example, only ~4000 VLAN tags. What happens when you have more
>> than that many customers?
> 
> If you're hanging 4K customers off the same switch, you probably have bigger
> issues than running out of VLAN tags...
> 
>> We are talking very, very, small customers here. SOHO to say the most.
>> /64 should be more than sufficient for their CPE router.
> 
> A Linksys WNDR3800 running CeroWRT (and probably OpenWRT by now) will prefer to
> create multiple /64's - one for the 4 wired ports, one for private access on the
> 2.4G radio, one for guest access on the 2.4, and another private/guest pair
> on the 5G radio. So there is CPE gear out there now that can blow through 5 /64s
> by default, and more if you enable VLANs.
> 
> A /56 allocated via DHCPv6-PD would be a *minimum*.  And prefixes are cheap,
> so you may as well hand them a /48, just in case they have a second WNDR3800
> at the other end of the building for coverage - because that one will then ask
> the upstream one for a -PD allocation.  So if you give the CPE a /48, it can
> keep a /56 for itself, and hand the downstream a /56, and they can each
> allocate /64s as needed.
> 
> And remember - prefixes are cheap and plentiful, so don't bother with /52
> or /60, just split on 8-bit boundaries to make life easier for yourself...
> 