IPv6

> One thing that is not clear to me if it is possible still possible to leave cable modem provisioning in IPv4 and assign IPv6 addresses only to subscribers' CPEs?

Yes.

Be aware that Windows users would need to be Vista or 7. IPv6 support in XP is via pretty bodgey add-on pack and I wouldnt recommend it.

Also keep in mind that most residential (and even corporate) routers do not yet have good support for IPv6

> Another question that bothers me. If there we've got a docsis 3.0 cmts and a docsis 2.0 cable modem, would it be possible to assign an IPv6 address to a CPE behind that docsis 2.0 cable modem?

No. Must be a DOCSIS 3.0 cable modem on a DOCSIS 3.0 CMTS

And something else to be aware of if you have Cisco CMTS..... On Cisco DOCSIS 3.0 CMTS, IPv6 is not yet done in hardware. You can provision and use IPv6 but there are performance limitations. It is explained in the small print here :

http://www.cisco.com/en/US/docs/ios/cable/configuration/guide/cmts_ipv6_...
"The IPv6 functionality on the Cisco uBR10012 router manages the CM and tests the infrastructure for CPE deployment. Cisco IOS Release 12.2(33)SCC does not support PXF acceleration of IPv6 data packets on the Cisco uBR10012 router platform. IPv6 data packets from CPE devices are handled by the control processor. Hence, the packets per second (pps) rate is limited to a few kpps per CMTS. IPv6 traffic of 3 kpps on PRE2 and 12 kpps on PRE4 produces an acceptable load on the Cisco uBR10012 control processor. "

So with SCC and SCD you can do a bit of testing but its not ready for prime time. I have been told it will move to hardware in SCE release.

Oh and another limitation I just remembered, there is no IPv6 Netflow support, which can be a problem if you are wanting to count user traffic