Re: Automatic IPv6 due to broadcast

[Chuck Anderson <cra () WPI EDU>]

On Mon, Apr 23, 2012 at 12:24:53AM -0700, Owen DeLong wrote:
> On Apr 22, 2012, at 10:30 PM, Jimmy Hess wrote:
> >   Particularly good L2 switches also have
> > DAI  or  "IP Source guard"  IPv4 functions,   which when properly
> > enabled,  can foil certain L2 ARP  and IPv4 source  address spoofing
> > attacks,  respectively.
>
> > e.g. Source IP address of packet does not match one of the DHCP leases
> > issued to that port -- then drop the packet.
>
> Meh... I can see many cases where that might be more of a bug than feature.
>
> Especially in environments where loops may be possible and the DHCP lease might
> have come over a different path than the port in question during some network event.

You're only supposed to use those features on the port directly
connected to the end-system, or to a few end-systems via an unmanaged
office switch that doesn't have redundant uplinks.  I.e. edge ports.