Ars Technica on IPv4 exhaustion

Owen DeLong owen at
Mon Jun 23 05:04:09 UTC 2014

On Jun 22, 2014, at 20:41 , Laszlo Hanyecz <laszlo at> wrote:

> On Jun 23, 2014, at 3:32 AM, "Kalnozols, Andris" <andris at> wrote:
>> On 6/22/2014 7:41 PM, Frank Bulk wrote:
>>> Did they ever explain why?  Did the SMC function as a router, and act as the
>>> customer side of a stub network that allowed that /29 to hang off the
>>> router?  If that was the case, and the Motorola D3 modem was L2-only, that
>>> might explain the change in capability. 
> The Comcast business SMC gateway speaks RIP to make the routed /29 work.. in theory it could be put into bridge mode and you can do the RIP yourself but they don't support that configuration (you'd need the key to configure it successfully and they didn't want to do when I asked).  If you poke around in the web UI, it does support IPv6 in some form, but it doesn't seem to be active for me.
> If you don't have a static IP block from them and thus don't have the need to use RIP you can just use a regular DOCSIS 3 cable modem and get IPv6, but you only get one IPv4 number that way.

In my experience, if you put a switch behind the modem (not a router), you can get as many IPv4 numbers as you have devices attached to the switch on Business Class. On residential, you're limited to one, but I have gotten multiples on business class.


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