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dcreedon

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DHCP

how can you find out where in the config a client knows what server to look at for an ip address?
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dcreedon

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what determines whether it goes to the primary or secondary dhcp server?
or  ifconfig if you are running *nix
why would a user be getting an ip from the secondary dhcp server? i presume it is good practice to have a primary and secondary dhcp server in case one of the servers goes down?
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dhcp is broadcast-based, and usually the first server to respond is the one that issues the address.  
i guess the event logs might be able to tell me which server first answers the request?
"ipconfig /all" should tell you which server is the one that issued you your address.  There shouldn't be any primary or secondary.  That's usually referred to for DNS servers.  Not DHCP.
so dhcp installed on one server is ok? i thought that if this server went down for any reason the server where the secondary dhcp installed would lease ip's?
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Just a side note. As long as you have a lease period set to a reasonable length of time, say 30 days, the DHCP server can be down for days and nobody would notice. A client does not even re-querry the  DHCP server until 1/2 of the lease time has expired. At that point, they begin a direct conversation - "hey, server, my lease is about up, how about I go ahead and re-new it now?" server: "OK, keep what you got"
no answer from server because it's down: "oh, well, I guess I'll just keep what I got and try again later"...

But if you only want it on two servers for backup reasons turn DHCP off on the backup server and only turn it back on if the primary server goes down.
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You don't want overlapping scopes EVEN IF YOU LEAVE THE "SECONDARY" TURNED OFF UNTIL THE "PRIMARY" FAILS, because there's no clean way for the backup to know what addresses the primary has already given out, and to whom.  (Some implementations try to use ping to determine if an address is in use, but some firewall products block answers to ping;  some security applications (labrea springs to mind) will answer ARP requests for unpopulated addresses, so you can't rely on that either.)

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