Greenfield IPv4 + IPv6 broadband deployment

Frank Bulk frnkblk at
Sat Feb 26 20:02:52 CET 2011


Best practices haven't been established for broadband deployment, though
there are a few informational RFCs that discuss a variety of approached.

In our network we have four physical access platforms (xDSL, FTTH (GPON),
cable broadband, and broadband wireless) and each of those is configured
differently: xDSL: mostly PPPoA, lot of PPPoE, and a few bridged; FTTH:
mostly 1:N, a few PPPoE left; cable broadband: all bridged; broadband
wireless: all bridged.

I've started with our FTTH first, and with the 1:N approach I already ran
into an issue with our access platform.  The mode that enforces L2
separation prevents stateful DHCPv6 from succeeding because multicast is
blocked.  The vendor is aware of the issue but a solution won't be GA until
Q4 at the earliest.  In the meantime I've configured trial customers with L2
separation turned off so that the multicast flows through.  Unfortunately I
can't scale L2-separation-off because the vendor has a limit of 210 such
subs per VLAN for other reasons.  I'm also waiting for LDRA support.  Going
to 1:1 would resolve all these issues, but that would mean purchasing an
ES+/ES20 card for our 7609-S and completely changing our approach.

I've chosen to use stateful DHCPv6 (with prefix delegation) because
CableLabs requires it (and might as well as make configuration as similar as
possible between access platforms) and so that I make it easier for us to
comply with CALEA requests and general tracking.  I'm assigning a dynamic
/56 to each broadband sub using a separate DHCP server for v6.  I haven't
tried any static prefix delegation, but I presume I can do that if I know
the customer's IAID (just like if I know the customer's WAN MAC)?  

That's as far as I am today.  It will be Q3 (at the earliest) before our
CMTS vendor has an IPv6-ready load for us to try.  I'm not sure if I'm going
to do bridged for our xDSL, but I will for our VDSL2.  Our broadband
wireless will be bridged.

If you have a certain access vendor in mind, I would strongly encourage you
to ask your sales engineer for advice on how to deploy IPv6 access on their
products and then test and scale it.  It's likely your sales engineer will
says "this is the first time anyone has asked me about this".


-----Original Message-----
From: at
[ at] On Behalf Of
Adam Armstrong
Sent: Saturday, February 26, 2011 12:07 PM
To: IPv6 operators forum
Subject: Greenfield IPv4 + IPv6 broadband deployment

Hi All,

I'm currently in the planning stages of a large scale broadband 
deployment, with the hopes of doing sane dual-stacked v4/v6 to every 
subscriber from day one.

I know the CPE issue has been talked about to death, and I'm pretty 
unhappy with the situation there at the moment, but for the time being 
I'm assuming CPE are not an issue.

All transport is ethernet, with subs being dragged back to a small 
number of central gateways. I'm looking at a mix of DHCP and DHCPv6-PD 
to distribute addresses. PPP isn't an option.

Is anyone else running a similar setup? Are there any recommendations on 
how to handle customers with static assignments?

Is it better to try to give every subscriber a static v6 assignment, to 
reduce issues with internal addressing?

Does anyone have any recommendations on how to manage many static v6 
assignments in a DHCP environment?

As I'm not dropping a v6 deployment on top of an existing v4 deployment, 
I'd like to make sure I've done it right for both.

Does anyone have any recommendations regarding 1:1 or 1:N VLAN models?

Thanks in advance,

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