Posted 29 December 2012 - 16:51
"DHCP shouldn't assign an IP to any device if another device on the network has that IP, be it static or Automatically Assign"
It shouldn't no - but its a VERY VERY BAD idea to setup static IPs on the host that fall within the dhcp scope.
So for example if your dhcp server hands out 192.168.1.100 to .150, and you want to setup a static on the host itself then it is better option to use 192.168.1.1 to 99, or .151 to .254
Keeping in mind whatever other statics you might have set, your routers static IP, etc.
Yes depending on your dhcp server and and even dhcp client, you should not hand out dupe IPs. Your dhcp server could check for them before it hands out, or even the client when gets an offer for specific IP can check to see if any other host has that IP and then send the dhcp server a decline message
Sent by a client to a specific server in response to a DHCPACK message, which contain parameters which the client has determined are not in fact valid. For example, the client might test an IP address it has received by sending an ARP (Address Resolution Protocol) message on its shared LAN to see if any other host has been assigned this address; if it discovers that another host is in fact using this address, it must send a DHCPDECLINE message to the server which supplied the address. This both allows the server to release the resources it has allocated to this client, and inform a system administrator of the problem. (Such a problem might arise in a situation in which a host has been manually configured by an administrator with an IP address, but the DHCP server hasn’t been informed that this address is no longer available in its pool. Though it is suggested that a server test an address before allocating it to a client [1, section 3.1, point 2], for example by “pinging” the address to see if another host is using it, it may be that the test or the response to it is lost, incorrectly suggesting to the server that the address is available.)
But not all dhcp clients support this, nor do all dhcp servers -- the dhcp servers in soho routers are normally very limited in features, etc..
Normally its a better idea to setup a reservation on your dhcp server to always hand out same IP to host normally based on its mac yes. This way host can get other updated info you might hand out in dhcp, dns, gateway, local domain, ntp server, etc. etc. But either works be it you set the static on the host or setup a reservation.