at&t business ipv6
nick at foobar.org
Thu Jun 21 16:07:48 UTC 2018
Randy Bush wrote on 21/06/2018 16:35:
> anyone been to this movie and care to divulge the plot?
Yes, one particular plotline which can explain why docsis systems do
this is that standard residential customers are provisioned using giant
broadcast domains directly on the cable, with DHCP config. Obviously
it's more complicated because it's docsis, but lemme handwave and say
that this is the gist of it. Because you're dealing with giant
broadcast domains, you assign IP address blocks to individual CMTSs and
your customers are assigned out of those ranges.
Assigning ipv6 in this context is really simple: it's part of the
baseline DOCSIS3.0 standard and is supported incredibly well by all
parts of the network.
Static addresses don't fit into this paradigm because you if you
configure your static customers from a single broadcast domain, then
they are glued to a particular CMTS and can't be moved from that CMTS
unless you renumber them.
This doesn't work in practice because if you want to grow your network,
you probably want to be able to move around chunks of your cable network
from one CMTS to another in order to balance out your traffic. Or you
might want to split a bunch of cable nodes from one CMTS to multiple,
according as your traffic outgrew the capabilities of a single CMTS (a
node in this context is a small chunk of a cable network).
One way of getting around this mess is to backhaul all your static
customer interfaces using mpls l2vpn PWHE up to a L3 box which just
handles static IP addresses. You configure the customer's static
default gateway IP address on an interface on this head-end router, and
the customer's cable modem will have a virtual connection directly to
that interface. The thing is, this virtual interface termination system
might or might not be tied into the entire ipv6 provisioning system. If
it isn't, you're SoL. So even if dirt-cheap residential customers can
get ipv6 very easily, it's different by virtue of the fact that you're
using static IP addresses, because they're a headache for cable operators.
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