DHCP Service running on Windows Server

Hi Guys,
I have a network where I have set up a DHCP Service in a Windows Server, and recently I have been asked what would happen if the Windows Server with the DHCP Service goes down?

Would all the computers (Windows 8) that have leased an IP address keep working or would they loose the IP and go back to a 169 default IP?

My understanding is that as long as the user doesn't restart the computer it will keep the leased IP, and so be able to connect to the network. Assuming that the lease doesn't expire of course.

We are talking about the DHCP Server being down let's say for 2 hours.

Am I right?
cargexAsked:
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BillBondoCommented:
You should have zero issues if only 2 hours. Basically you are correct in your thoughts. Unless you lease times are 15 minutes...
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Thomas GrassiSystems AdministratorCommented:
Another thought would be to setup  a failover DHCP Server.

with Windows Server 2012 you have that option available

Works great for IPV4 addresses

And again yes the ip address will remain unless they reboot
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Neil RussellTechnical Development LeadCommented:
But don't forget that any device not on when you take down the server will not now be able to boot onto the network until either a) Your DHCP Server is back online -or- b) You give it a static address.
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vivigattCommented:
DHCP client ask to renew their lease when it has half expired.
In order to be sure not to have too many issues with a 2 hours down-time, I would then suggest that your DHCP settings be so that the lease is long enough.
But you can't be sure that no client will send a dhcp lease renewal request while your DHCP server is down, unless you force them to send a renewal request (ipconfig /renew command) just before taking the server down.
DHCP failover is something to think about.
You could also have a split-scope second (backup) DHCP server for the time being (or even for every day operations):
https://technet.microsoft.com/fr-fr/library/Ee405264%28v=WS.10%29.aspx
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D_VanteCommented:
run two DHCP and two DNS servers to avoid issues
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Mal OsborneAlpha GeekCommented:
The usual default DHCP lease time under Windows is 8 days. Client machines will try to renew after 4 days (lease half expired), so you should have at least 4 days grace.  If a Windows machine boots on a network with a valid lease, it will try to ping the default gateway, ping itself and assuming it gets a response to the former and not the latter, continue to use that IP.  

2hours of downtime should not matter.
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cargexAuthor Commented:
Thank you very much Guys, in summary:

I will make sure all my clients get a renew before the possible event of having the DHCP Server down happens, and that way I will avoid any issues with leases expiring during the down time.

Only the computers that are on when the event happens will keep their lease.

Create a plan for a DHCP failover.
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