IPv6 Subscriber Access Deployments

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Tue Sep 8 19:54:50 UTC 2015


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...

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