Fwd: Rapid DHCP

[Richard W.M. Jones]

On Sun, Jul 31, 2011 at 12:35:29AM -0400, Chuck Anderson wrote:
> On Sat, Jul 30, 2011 at 11:30:30PM -0400, Genes MailLists wrote:
> > On 07/30/2011 06:49 PM, Dan Williams wrote:
> > > What's unique about the method described there is that the Mac
> > > configures the interface with the same IP address it previously had if
> > > the lease is still valid, while NetworkManager waits for the DHCP server
> > > confirm the lease.  So we could presumptuously configure the interface
> > > with the previous address from the lease and then only tear it down if
> > > the DHCP server fails or rejects the renewal.
> > 
> >   Probably best not to do this - as it can lead to duplicate IP's on the
> > network - even if briefly - wasn't something like this an issue with
> > some smartphones and princeton univ wifi - and led to them banning
> > android for whatever version had the problem ?
> 
> No, it cannot lead to duplicate IPs *if the lease is still valid*.  If
> the client has a cached lease, and the lease has not yet reached
> expiry, then the promise that the DHCP server has made to that client
> for it to use that IP address for that period of time is still valid
> and the client is free to continue use that IP address.

Most (broken) domestic routers forget the DHCP leases they gave out
after being rebooted.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v