Question about 6to4

Jay Hennigan jay at
Sat May 16 16:00:34 CEST 2009

Martin List-Petersen wrote:

> Well, DHCPv6 is not very common yet. Most routers will do
> route-advertisements. We even got Mikrotik to support the advertisement
> of nameservers via rdnssd, which actually also make that a fully usually
> auto-configuration then.
> I spoke to AVM at CeBIT, and they are planning on doing DHCPv6 for the
> Fritz! box family, but it's not in there yet. Currently it's
> route-advertisements only.
> Also be aware, that you can't use DHCPv6 only. You need
> route-advertisements, too, because DHCPv6 doesn't set a default gateway.

Yes, I'm aware.  The problem I'm trying to solve relates to a discussion 
on the NANOG list regarding subnet size for DSL small office and home 
users.  There's discussion regarding /56 vs /48 but pretty much everyone 
agrees that home DSL users should get more than just a /64.  We concur, 
and opted for /56.

The goal is that the customer's CPE will learn the /56 (or /48) from our 
provider edge router and then assign a /64 from within that space to 
each customer LAN subnet automatically.  We're doing this now with early 
adopters using DHCPv6 and Cisco gear, typically refurbished 8xx and 1721 
series.  This doesn't scale from a price and support perspective.  If 
there is a way to accomplish this without a DHCPv6 client in the home 
router, I'm all ears.  I openly confess to being a newbie with regard to 
IPv6, but I think we're ahead of the curve with respect to most ISPs in 
the US.

Just router advertisements seems to work if we assign a /64 and there is 
one subnet with a simple switch or bridge at the customer end but this 
doesn't scale or play well in a dual-stack scenario as straight IPv6 
bridged pass-through coupled with an IPv4 NAT scenario on the same CPE 
doesn't seem to be supported by any existing CPE.  This method only 
allows for a single /64 to the customer as well, which we're trying to 

Jay Hennigan - CCIE #7880 - Network Engineering - jay at
Impulse Internet Service  -
Your local telephone and internet company - 805 884-6323 - WB6RDV

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