v6 subnet size for DSL & leased line customers

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Thu Dec 27 12:19:47 UTC 2007

On Thu, 27 Dec 2007 12:11:54 +0100
Iljitsch van Beijnum <iljitsch at muada.com> wrote:

> On 27 dec 2007, at 11:57, sthaug at nethelp.no wrote:
> > "Configure this stuff manually" may work for a small number of
> > customers. It is highly undesirable (and probably won't be considered
> > at all) in an environment with, say, 1 million customers.
> Of course not. But RAs on a subnet with a million customers doesn't  
> work either, nor does DHCP on a subnet with a million customers.
> If we're talking about provisioning cable/DSL/FTTH users, that's a  
> completely different thing. Here, DHCPv6 prefix delegation to a CPE  
> which then provides configuration to hosts on its LAN side would be  
> the most appropriate option. However, the specifics of that model need  
> to be worked out as there are currently no ISPs and no CPEs that do  
> that, as far as I know.

I haven't had a chance to test it, but according to "Deploying IPv6
Networks", IOS can support DHCPv6 based prefix delegation. It even
supports multiple downstream interfaces on the CPE - you configure the
subnet number you want on each of the interfaces, and the CPE will
configure the DHCP-PD learned /48 on the front of them automatically
and then start announcing those prefixes in RAs out those interfaces.



        "Sheep are slow and tasty, and therefore must remain constantly
                                   - Bruce Schneier, "Beyond Fear"

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