On Apr 23, 2012, at 6:25 AM, Chuck Anderson wrote: > 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.
In a lot of cases, enforcing that all address assignments are via DHCP can still be counter-productive. Especially in IPv6. Owen
