DHCP Redundancy and Reservations

Posted on 2006-03-23
Last Modified: 2007-12-19
Okay I have 2 Windows 2003 DHCP Servers.   I have reservations set up for .2, .3, .4, and .5 IP Addresses.  If I set up the reservations in both DHCP Servers I get an IP Policy conflict.  If I set up the servers to give out different IP address ranges the reserved clients will receive the IP from the DHCP server without the reservations.  The same goes if I set up reservations on one server and not on the other.  

What I end up doing is diabling the DHCP server without the reservation then rebooting the client the starting the DHCP server again.  

I would like to have the fault tolerance for both DHCP servers with my reservations and without having to start and stop the DHCP service.  

Thank you for your help

Question by:rbradberry
    LVL 15

    Expert Comment

    you cannot have two DHCP servers with the same active scopes - there has to be an exclusion range set, otherwise both servers will hand out the same IPs, because they do not synch with one another, they only go off the information in their own database.  here is a good forum post about creating dhcp redundancy:

    LVL 3

    Author Comment

    but if i set a reservations on one server 1 and exclusions on server 2 then server 2 will just give the client a non excluded ip address but wont give it the reserved one.
    LVL 1

    Accepted Solution

    Normally with DHCP you would have 2 servers using what is called 80/20 address space leases, meaning 80% of a scope/subnet on one box Primary and 20% of a scope/subnet on a second box Secondary. You can of course alter this ratio. As far as reservations go you should be able to get those areas to overlap on the 2 servers because reserved DHCP addresses cant conflict if you follow me.

    LVL 1

    Expert Comment

    I think you can do what i just mentioned with super scopes....

    LVL 3

    Author Comment

    so basically I set up my superscopes to be:

    so if I set up server 1 with the first 80% and server 2 with the remaining 20%, and the reservation is given on server 1.  Can I set that reservation on server 2 so that server 2 doesn't give it one of it's available IP addresses?

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