Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I am trying to figure out which computer may have an IP is there anything that might help me besides the following:

  • nmap just shows tcp 3001 open, I have tried throwing some text at that with telnet, but its not responding.
  • The MAC address Vendor doesn't help me
  • I currently don't have access to the switch
  • No ptr / DNS record
share|improve this question
up vote 4 down vote accepted

The switch MAC database is the best way to do non-intrusively, but since you say you can't get there, you're going to have to tear things apart.

Start pulling the network apart, piece by piece and, as you do that, attempt to PING the device between changes. Disconnect Ethernet switches until you can make the offending host stop answering. (If it doesn't respond to PING, clear your ARP cache and attempt to PING it. It'll probably answer for ARP even if it doesn't answer for PING.)

Once you narrow it down to a given switch, I'd recommend doing a binary search to pinpoint it as quickly as possible (disconnect half the cables, see if it's there, disconnect half of the half where it was located, repeate until you locate the offending device).

What's the MAC address, if you don't mind me asking?

share|improve this answer
00-20-4A-..... PRONET GMBH – Kyle Brandt Dec 9 '09 at 18:22
I guess that might help, Desktop / Server NIC? – Kyle Brandt Dec 9 '09 at 18:24
Lots of sub-ms pings that could tell me the distance over time? :-P – Kyle Brandt Dec 9 '09 at 18:27
So it's probably an embedded device-- SCADA gear, like a PLC or some such. Lantronix owns Pronet Gmbh, so it might have a Lantronix name on it. Could be a Lantronix print server or serial over Ethernet device, too. No such luck re: PING response times... heh heh... – Evan Anderson Dec 9 '09 at 18:32
It is a Lantronix timeclock :-) – Kyle Brandt Dec 9 '09 at 18:32

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.