Charter ARP Leak

Brett Frankenberger rbf at
Mon Dec 29 17:35:42 UTC 2014

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
  ip address secondary
  ip address secondary

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

Doing it over a CMTS doesn't change that.

     -- Brett

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