[TriLUG] Windows DHCP to ISC DHCP migration

[Joseph Mack NA3T]

On Wed, 24 Oct 2007, Shawn Hood wrote:

> 3) Shorten the lease time to a very small number, wait for all workstations
> to cycle.  Shut off the Windows DHCP and startup Linux.

I'm with Chris.

You don't get a lot of choice with lease time. Windows 
machines only ask for 5mins, even if you allow a longer 
lease time. Linux machines ask for an hour. I suspect a 
windows dhcpd will only grant a 5 min lease. So the 
changeover has to occur in a time less than 
5mins/number_clients.

However dhcpds don't tread on each other's toes. If you have 
two of them running, when the client asks for an IP, it will 
only accept a reply from one machine. The dhcpd will not 
grant a lease for an IP which it thinks is free (from its 
leases file) if there is a machine with that IP on the 
network. (I think) you only need to two dhcpds to cooperate 
if you've coupled the dhcpd to DNS.

So test your linux dhcpd machine off-line, then plug it into 
the network of interest and then bring down the windows 
dhcpd. The clients shouldn't know that the dhcpd server has 
changed.

(I haven't done this - this is just my best guess)

Joe
-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!