Client not recieiving IP When DHCP Server down..

Posted on 2009-02-23
Last Modified: 2013-12-23
I have a windows 2000 Server sp4 as a DHCP Server in single domain with about 200 clients. Client lease 5 days duration, most clients are on dynamic ip setting.
We had a power cut and dhcp server went offline, while offline some of the clients who were connected are now not able to connect to network as dhcp server was not found. from my knowledge as the lease duration is set to 5 days all client should still able to hold of same ip addresses unless the client expires lease duration.
Please explain as why client lost connectivity while DHCP server was offline.

2) From above scenario, is it possible to have 2 dhcp server for fault tolerant, if server A not available then Server B will release ip addreses.
3) Any third party tool for dhcp fault tolerant and alerting systems administrator will be a bonus.

Question by:PeterMatthews
    LVL 82

    Accepted Solution

    1. DHCP clients are automatically trying to renew their lease after half of the lease time has expired (every 2.5 days in your case). So if a client has been left running, and tried to renew its lease at the moment when your DHCP server went down, it will have an obvious problem.
    2. Yes, but these two servers have to have non-overlapping scopes in the same subnet!
    3. You could use a clustered DHCP server (but that's too expensive just for DHCP, so just consider it if you have a cluster system anyway), or a virtualized DHCP server running on two independent nodes with "failover move" capability.
    But note that neither setting up several servers nor a cluster (MSCS or virtual servers) will help you any if a power cut will shut down all servers at the same time.
    It's better to invest into a UPS solution.

    Author Comment

    1) Can you please reccommend a easy solution if dhcp server is down it will not affect any users.
    in my mind increasing the lease to 10 days or moving to static ip is the only solution.
    2) from your above answer,  "client will renew auto after half of lease time"..
    My server lease duration is set to 5 days and dhcp server was offline for 30 mins, it affected few users with no network connectivity. Once dhcp was back online everything was in working order.

    Could you please me?

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