Re: Two DHCP setup in mix windows 2003 network.
From: Miha Pihler [MVP] (mihap-news_at_atlantis.si)
Date: 03/16/05
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Date: Wed, 16 Mar 2005 08:20:23 +0100
Hi,
Yes this is correct and expected behavior if you shut down client computer
and DHCP server...
Again, lease of 7 days does not mean the client will hold to that IP address
for better or worse. What lease time does is it reserves IP address for the
client (for client's MAC address) in DHCP database. In those 7 days (or even
more since client can renew the lease) only this client will receive the IP
address that was reserved, but client must be able to contact the DHCP
server.
Imagine if the client was holding on to the IP address. Now I take my laptop
from company network with different IP subnet to my home or my client's
network. The client boots up and has IP address from my office network. This
could either cause conflicts if the client's network used same IP address
space (since another computer could be on the network that uses same IP
address) or it would by default prevent me to communicate with anything else
on the network since the client or my home network use different IP address
space. Now I would have to go and run "ipconfig /release and ipconfig
/renew" to get the IP address that would work on my network (pretty
inconvenient).
When I return to office network and computer boots up it will contact DHCP
and it will assign the client same IP address that was e.g. least to it this
morning and it will continue to do this for next 7 days (or more).
Another thing that will lease do for a client is in case of DHCP failure it
will allow client to keep the IP address for lease period (e.g. 7 days) as
long as you don't shut down the client.
Client will try to renew the lease after 50% of lease time is up and it will
continue to try and renew the lease. If it can't connect to DHCP server it
will start DHCP discovery process (to see if there are any others DHCP
servers that it could use) after the lease is up (e.g. 7 days).
To avoid problems with single DHCP failure you should setup at least two
servers with DHCP service.
-- Mike Microsoft MVP - Windows Security "IT Boy" <ITBoy@discussions.microsoft.com> wrote in message news:CDBC907C-E432-410E-8A00-53C659B7CDF0@microsoft.com... > Thank for explaining. > I think, I had not make it clear, > What I went to ask is does the client, still used that IP, (e.g. an > client, > release and renew IP, then shutdown. Now shutdown the DHCP, Power back up > the > client PC it IP will come to 169.x.x.x) Is this right ? Lease time on DHCP > set to 7 Days. > > Thank again, I am just alot of not understanding... > > S. > > "Miha Pihler [MVP]" wrote: > >> Lease time does not mean how long client will hold that IP address. Lease >> time means how long will IP be reserved on the DHCP server for that >> client >> (for that MAC address). Within that lease period client will receive same >> IP >> address from the DHCP server that issued IP address... >> >> Clients will also try to renew lease after 50% of lease time is up and >> will >> try to renew till the lease is up. After the lease is up it will try to >> discover any other DHCP servers on the network. >> >> -- >> Mike >> Microsoft MVP - Windows Security >> >> >> "IT Boy" <shingxx@Hotmail.com> wrote in message >> news:ux4RnCXKFHA.3552@TK2MSFTNGP12.phx.gbl... >> > Hi, >> > >> > I think I had got it working for unknown reason. >> > I am using DHCP 1 range: 144.1.1.100 to 144.1.1.150 >> > Now DHCP 2 range: 144.1.8.100 to 144.1.8.150 >> > Now is working! stopping DHCP 1, client will obtain from DHCP 2. >> > But before I had try on DHCP 2 range: 144.1.3.100 to 144.1.3.150 this >> > does >> > not work. I will try again later. >> > >> > Other information: >> > Default gateway: 144.1.0.254 >> > SM: 255.255.0.0 >> > IP of servers : 144.1.0.10 and 144.1.0.20 >> > >> > So I think the two DHCPs is working now, >> > >> > But the other problem, now I face with is that clients could not keep >> > it >> > lease of IP. >> > With an 7 days lease, each time an client power down or reboot it renew >> > it >> > lease! >> > >> > What should I look for now? >> > >> > Thank for your help... >> > >> > S. >> > >> >
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