Re: IPv6 Subscriber Access Deployments

[Owen DeLong <owen () delong com>]

Short answer to that is “DHCPv6-PD”

Longer answer:

Customer’s router should get an address on the external interface through one of SLAAC, DHCP-PD, Static Assignment, 
depending on how the ISP prefers to do this.

If the ISPs equipment supports IPv6 on shared VLANs with DHCP snooping and other security, you can implement it with a 
single /64 giving each router a unique address within that segment, but it’s not really ideal. This was mainly done in 
IPv4 to conserve addresses. Separate point to point VLANs are a cleaner solution and since there are enough addresses 
in IPv6 to do this, that is how most providers implement. I prefer using /64s (or at least assigning /64s) to these 
VLANs, but there are those who argue for /127, some equipment is broken and requires a /126, and yet others argue for 
other nonsensical prefixes.

Once the router has an external address communicating point to point with the ISP router, it should then send an 
DHCPv6-PD request asking for a prefix that it can manage. The ISPs DHCP server should then send back a /48 (or if you 
want to be silly, a /56 or a /60, and if you want to be insane, a /64).

The reality is that if you send a smaller prefix back, you risk having difficulty with your future ARIN applications as 
your Provider Allocation Unit is based on the smallest prefix you delegate to end-users. So if you, for example, assign 
/48 to business customers and /60 to residential customers, you’re going to have to justify why each of your business 
customers needed 4096 /60s when you claim that you need more IPv6 space.

OTOH, if you simply issue /48s to everyone, you can just go back and say “Each end site got a /48 and there are N 
end-sites” and you’re good, no questions asked about the size of any of those end-sites.

Owen

> On Sep 8, 2015, at 12:12 , Josh Moore <jmoore () atcnetworks net> wrote:
>
> We are talking a purely bridged environment. However, I have been wondering how in the world end-to-end IPv6 
> connectivity is supposed to work if a customer hooks up their own router. That is one of the points of IPv6...
>
>
>
>
> Joshua Moore
> Network Engineer
> ATC Broadband
> 912.632.3161 - O | 912.218.3720 - M
>
>
> -----Original Message-----
> From: Valdis.Kletnieks () vt edu [mailto:Valdis.Kletnieks () vt edu] 
> Sent: Tuesday, September 08, 2015 3:08 PM
> To: Josh Moore
> Cc: nanog () nanog org
> Subject: Re: IPv6 Subscriber Access Deployments
>
> On Tue, 08 Sep 2015 19:04:06 -0000, Josh Moore said:
> > I'm reading that the recommended method for assigning IPv6 addresses to end-users is to do this via a dedicated VLAN 
> > and /64.
>
> Important question - are you talking about the IPv6 address supplied to the CPE router itself, or a /48 or /56 
> delegated to the CPE router to allocate to subnets and devices behind it?