3.1.1 Failover Speed (was: Re: 4.1.0a1 Failover sync speed)

[Simon Hobson]

Glenn Satchell wrote:

>  >This may have been true once, but we tested this: setup a subnet with
>>a "range 10.10.10.4 10.10.10.5" and assigned '.4 fixed. We joined two
>>machines, neither of which were the MAC assigned '.4, and no other
>>machines were on the subnet at all. The first was assigned .5, the
>>second just generated a 'no addresses available' error.
>
>Umm, not necessarily. dhcpd sends a ping before offering the address to
>make sure it is free. If it gets a response then it will abandon that
>address and not attempt to re-use it until it has no other available
>leases.

And of course, many devices no longer respond to pings - IIRC XP SP2 
configured the firewall by default to block pings, thus making XP SP2 
(by far the commonest client I would imagine) invisible to this check.