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How is it that on a local area network with a router that allows IP address reservations (exempting the special situation that a static address is assigned to the different device) that a completely unrelated device can still grab and use the reserved address?

I have several servers on my LAN that I've assigned reserved addresses to. All of a sudden this morning my media server went offline. After eliminating other possibilities I found that SOMEHOW in the recent past another device appropriated that address so when I checked the server and hit reassign I got a completely different IP address. I was finally able to resolve the issue. I understand this is common. Outside manually assigning a conflicting address (which I don't do) how can I avoid this? It pretty much negates what you think you are achieving with a reserved address.

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    Do you happen to have multiple places where DHCP would be enabled, such as on two routers or a stand-alone DHCP Server?
    – Allen Howard
    Commented Sep 20, 2018 at 14:39

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Perhaps contact with the computer was cut for some reason. Perhaps the router and other devices rebooted because of a power surge, IP addresses were re-allocated and there was an overlap between the allocated range and the reserved IP addresses.

I suggest to verify the settings of the router as regarding DHCP. The router's DHCP server should not be allowed to allocate IP addresses that conflict with the reserved ones.

For example, allow the router to allocate addresses between 100 and 200, and allocate all reserved IP addresses from the range of 2 to 99.

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    Ahh, that has to be it. Like everyone my network goes down from time to time but I only have a handful of servers with reserved addresses and I suppose I've just been lucky in the past with the random order of things coming back online. I'm going to take your advice and pull out a series of addresses solely for reservation and allow DHCP to do the rest. It had to happen to me once to see that it is necessary. Good answer. I can't vote up yet but I'll work toward it. Thank you.
    – CharlieX
    Commented Sep 20, 2018 at 16:51
  • You can surely accept the answer on your own post (the V button).
    – harrymc
    Commented Sep 20, 2018 at 18:00

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