DNS Issues

[Gerald Combs]

On Thu, 6 Jun 2002, chuckx wrote:

> > I suspect 
> > they are using port monitoring to identify my first 48 bit NIC 
> > address and when they see packets with another NIC address, they 
> > refuse the DHCP request and I can't direct connect another system to 
> > my cable modem, thus I use NAT through the router to keep both my 
> > systems up and on line.  Pretty slick and easy to administer.
> 
> What you described is just about right.  Once you reach the maximum number
> of clients your modem is configured for, network traffic from additional
> hosts is not passed on to the cable network by the cable modem.  Notice that
> your connection is not being actively monitored though.  Your cable modem is
> a just network bridge that is configured to pass network traffic for a
> limited number of hosts.  The modem does keep track of the hosts connected
> to it via their MAC addresses.

If RR is running Cisco uBR equipment (and I'm pretty sure they are),
they can block this at their end of the connection with the one-liner
'cable max-cpe 1':

  http://www.cisco.com/univercd/cc/td/doc/product/cable/bbccmref/bbcmts.htm#xtocid42

The above link is an interesting read.  They can mess with your cable
connection in all sorts of odd and interesting ways.