|Hmmm could be firewall is blocking ICMP request. But what about "nbtstat -a [ip address], does it also use ICMP or something else to get the netBIOS name??|
To be honest, I'm not sure if the nbtstat command is ICMP based but I suspect you have a firewall blocking that too.
While I am scanning with IPScanner, it's even showing dead.
Port scanning is one of the many things firewalls were invented to block.
I have a network of about 200 users and I have assigned static IP. I have the list of almost all the IP, I've assigned to the user and those IP's are not on that list as well.....
If I'm reading this right, the offending IP is not a "legitimate" IP as assigned by you. NOTE: I see you said. "I have a list of almost all the IP". You need to keep a list of all IP's you've assigned. There's no excuse for not doing so. Once the list is complete it's a simple and quick matter to add a new computer to the list.
This tells me you have some smarty pants cracker jack who's brought a computer up that isn't one that should be running. If it were me, I'd get the big boss man in charge and I'd do a walkaround when all staff are gone. Popping open a command prompt window and typing ipconfig /all on all computers in the building, while tedious and slow, would eventually yield the offending computer(s).
I would make note and then the next day, quietly find out who's using that computer and I would fire them on the spot. The phrase is, "terminated with prejudice". Disable their domain account, remove all access cards/keys and escort them off the property.
In fact, I would take it one step further. Once I've discovered the computer that isn't supposed to be running on my network, I'd find out what's going on on that computer. From the sounds of it, you have someone running sharing software and trading in illegal files. If that's the case, I'd see that they get escorted out the front door and into the waiting hands of the police.
This is the exact reason businesses have an "Appropriate Use" policy that applies to the companies computers and network. If you don't have one you need to make one and have all employees read it and sign a sheet stating they have read, and understood it. If you do have one, the person in question may also be liable for a computer hacking charge as well as the trafficking in illegal files (be it software, movies, music, kiddie porn etc).
Whatever is going on, if it's what I think it is, you need to stomp on this hard and make a big example of the person involved and then make sure all employees know why the person got canned.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.