Re: Charter ARP Leak

[Brett Frankenberger <rbf () rbfnet com>]

On Mon, Dec 29, 2014 at 12:27:04PM -0500, Jay Ashworth wrote:
> > Valdis, you are correct. What your seeing is caused by multiple IP
> > blocks being assigned to the same CMTS interface.
>
> Am I incorrect, though, in believing that ARP packets should only be visible
> within a broadcast domain, 

broadcast domain != subnet

> and that because of that, they should not be
> being passed through a cablemodem attached to such a CMTS interface unless
> they're within the IP network in which that interface lives (which is
> probably not 0/0)? 
>
> This sounds like a firmware bug in either the CMTS or the cablemodem.

int ethernet 0/0
  ip address 10.0.0.1 255.255.0.0
  ip address 11.0.0.1 255.255.0.0 secondary
  ip address 12.0.0.1 255.255.0.0 secondary

The broadcast domain will have ARP broadcasts for all three subnets.

Doing it over a CMTS doesn't change that.

     -- Brett