Residential subscribers: numbered or unnumbered?

[Sander Steffann]

Hi Philip,

> Until recently, I was under the impression that most people were using numbered v6 links to residential subscribers, allocating the WAN address using DHCPv6.  However, recently two people have told me about a number of providers that are doing unnumbered instead.
> 
> So for anyone who has deployed or is planning to deploy residential IPv6, I am curious to know which way you are going, and more importantly why you selected that approach? My interest is primarily in IPoE, but I don't mind hearing about PPPoE as well.

I'm doing unnumbered PPPoE to residential, which works fine. Each customer gets a prefix through DHCPv6-PD. The PPPoE routers (ASR1k) talk DHCPv6-PD to the customer and RADIUS to our management system. It automatically injects the route for the delegated prefix towards the link + link-local address of the customer.

The reason for this is simplicity in the addressing plan. This way we have one prefix per customer, which we completely delegate to them. If the link was numbered we would need another /64 for the link. Which would mean that we have to assign and track two prefixes to each customer: the link /64 and the delegated /56. We would very probably never see any traffic from the /64, but we do need to track it (legal stuff etc).

> Additional questions for those who have chosen the unnumbered approach or are using SLAAC to number the WAN address.
> * What are you doing wrt having an address to ping to confirm the CPE is reachable?

The CPEs we give to customers have a pingable address from the delegated prefix (prefix::1). And we can always see if the CPE is online by checking the PPPoE session.

> * For those doing unnumbered, do all CPEs implement the same algorithm for selecting the loopback address according to WAA-7 in RFC 7084?

As far as I know: yes. Almost all customers use the CPE that we provide though, so I might just be lucky :)

Cheers,
Sander