DOCSIS 3.0 & PPPoE/L2TP compatibility

Wed Aug 1 00:03:44 UTC 2012

Hi iptech

As others have said, early Cisco CMTS could do full bridging and/or PPPoE
termination, but newer gear is typically L3 style only.

For wholesale, the cableco could do one of these :

* L2 solution : Change your customers to configured as DOCSIS BSoD L2VPN,
and deliver you one dot1q VLAN per customer. You can continue to use PPPoE
with this config (sessions landing directly on your LNS). Gotcha: don't know
about Arris, but Cisco caps you at 4K VLANs per chassis which means this
solution doesn't scale all that well.

* L2 solution : Change your customers to be setup as DOCSIS BSoD L2VPN, and
deliver you one MPLS pseudowire per customer. You can continue to use PPPoE
with this config (sessions landing directly on your LNS). Gotcha: don't know
about Arris, but Cisco caps you at 16K pw per chassis which means this
solution only provides moderate scaling. Also you have to somehow terminate
all these pw (which are "xconnect"s in Cisco-speak).

* L3 soution : change your customers to land on a dedicated bundle and VRF.
Apply policy based routing to force-forward all the CPE traffic up a VLAN to
you. If you want to be able to authenticate/count/shape then you probably
need to terminate this traffic as IPoE (Use a dedicated BNG, or maybe you
could try Cisco ISG). Cableco would provide the DHCP for the CM, you would
provide the DHCP for the CPE. CMTS would insert CM MAC as option 82 so you
know which CPE belongs to which CM/customer. 

* L3 solution : last option is to do what they proposed. I would probably
still implement this with a dedicated bundle and VRF. But rather than having
to land the sessions as IPoE, you can now have them come in as PPTP. This
allows you to authenticate/count/shape via your LNS.

Hope that helps,
Michael.