Automatic IPv6 due to broadcast

Chuck Anderson cra at WPI.EDU
Mon Apr 23 10:23:14 CDT 2012


On Mon, Apr 23, 2012 at 06:38:09AM -0700, Owen DeLong wrote:
>
> 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.

If a specific managed environment provides DHCPv6 and doesn't provide
SLAAC, and the policies of said environment forbid static addressing,
how can enforcing the use of DHCPv6 be counter-productive?



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