unknown IP Address randomly pop up in the LAN creating IP conflict

for months we were confused by IP address conflict happened with our servers (we are implementing static IP in our LAN). So like usual we were trying to locate what was the culprit. to make it easier for us we just use the portable software netscan.
the software found the address, but can’t extract the information about the device, it just blank…
since we cannot determine which device it was, we can do several steps either by turning off the DHCP server, putting static IPs on every device, making several sub network (need routing table and own switch/router per sub network).
anyway since the bosses are not too fond of tinkering their gadget, we were not allowed to do the above method, too unpractical they said…
Ok, since they hold the bread and butter for my home, then I was forced to do the “manual labor”, checking every device that not smart enough to left out an identification on our network…
after randomly shooting and doing some research on the net, It just hit my head that we can identify the device by scanning (you can do it manually by using telnet, useless though if it was firewalled) the open port. and bingo! we found that the port 80 were open.

we then open the browser and entering the IP Address, and you know what? It turned out to be a DLink Print server.
And that leaves us with more mystery, since we already put the static address to the device through print server application (PS-Admin). Anyway, we continue to see the detailed network configuration on the device, and it turned out (again) that this print server can have two IP Address, one is for its UPnP (?Universal Plug n Play?) connection.
so we disable the UPnP function and save the configuration…

++++problem solved+++


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