Consider two scenarios:

  1. The end user has a simple computer, dual-stack

  2. The end user has a LAN behind a dual-stack router

How will ISPs differentiate each one of these kind of users in IPv6?

An user in scenario (1) would receive a single IP, whereas an user in scenario (2) would receive a /64 subnet (not sure if I'm correct on this one).

Will ISPs create 2 kinds of services (one for single IPs and one for subnets)? How does stateless auto configuration play a role here?

2 Answers 2


This depends on the class of service being offered. One gets assigned via stateless autoconfig, DHCPv6, or straight up static assignment, the other gets assigned a /64 or bigger. There isn't much difference here. In the v4 world it'd be one IP address and a /29 for the two classes of service, which the ISP is already doing.

The likes of Comcast, residential IP supplier for a large hunk of the US, is planning on passing out a /64 subnet to each subscriber rather than the single IP address they're handing out now.

IPv6 doesn't change anything here. Statically/dynamically assigned single IP addresses will continue to be served from the ISP's netblock, routable blocks will continue to be passed to customer equipment for further routing. It's just that the addresses are bigger.

  • Can confirm that my residential provider here in AU (Internode) is also handing out /64's already to people who want them. Re: single addresses though, how many ISP's will hand out individual addresses? From all the conversations I've seen, NAT was only really to help sort out the shortage in the IPv4 address space. Mar 15, 2012 at 5:59
  • I have the impression that even though ISP assigns subnets to end users, the protocols would act different here. In a IPv4 network, an user with a router would turn on DHCP relay in order to other nodes behind this router have IPs assigned. In a IPv6 network, there is no need for DHCP (in most cases) as a node can be autoconfigured using NDP. Is that correct? Mar 15, 2012 at 19:31
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    Handing out •one* /64 to each customer is very bad practice. A /56 or /48 per customer is normal. A /60 per customer is acceptable when deploying 6rd or something like that. Each home should be able to create multiple networks (home, work, guests, wireless, etc). Mar 15, 2012 at 22:52
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    kidbomb: The protocols are different. Configuring addresses for the directly connected device can be roughly the same as with IPv4, but IPv6 adds DHCPv6-PD for delegating addresses for the LANs. There is no NAT in IPv6, so just giving a WAN address to a router won't enable the devices behind it to access the internet. (See answer below for more detail) Mar 15, 2012 at 22:55

There potentially multiple networks here. First the network between the ISP and the user. There the addresses are provisioned with SLAAC (Stateless Address AutoConfiguration) and/or DHCPv6. This address (or these addresses, it's very normal with IPv6 for a device to have multiple addresses) is used by the device connected directly to the ISP (directly connected PC or a router). If a router is used it will request a block of IPv6 addresses for use on the LANs behind the router using DHCPv6-PD (Prefix Delegation). Those addresses can then be used by the router to assign addresses to LANs so that devices connected there can get their own IPv6 addresses.

  • The DHCPv6-PD prefix you get from your ISP is usually a /48 or a /56. Enough for 65536 or 256 subnets. Mar 15, 2012 at 16:54
  • LANs almost always get a /64 each Mar 15, 2012 at 16:55
  • What CPE routers out there support DHCPv6 prefix deligation? I'm having trouble finding any. We use a Vyatta Core router in a virtual machine in our lab at the office, but even it does not seem to support DHCPv6-PD as a client (although it can act as a DCHPv6 server with prefix delegation).
    – rmalayter
    Apr 27, 2012 at 13:00
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    I have seen DHCPv6-PD clients on Linksys, D-Link, Draytek, Netgear, Apple (AirPort Extreme and TimeCapsule), Zyxel, Technicolor/Thompson (beta software), Sitecom (beta) and some others that I can't remember at the moment :-) May 4, 2012 at 18:00
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    From James Woodyatt himself (linkedin.com/in/jhwoodyatt): lists.apple.com/archives/Ipv6-dev/2009/Oct/msg00086.html. If you look at his recommendations you'll see that "James wrote code that runs in Apple's AirPort wireless access points." so he seems to know what he is talking about :-) May 28, 2012 at 8:11

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