Server Fault is a question and answer site for system and network administrators. It's 100% free, no registration required.

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 bought an used Lantronix Spider and I cant seem to see it on my network (from my routers dhcp table). So my idea is that the device is not configured to use DHCP and assigned a static IP instead ... most likely on a different subnet than the one I'm using. The unit can be reset to factory default, however it requires a cable that I do not have.

So my question is whether or not it is possible to find a device with a static IP on a different subnet, on my network? I've got the MAC address of the device, but that's pretty much it.

Network setup:

DSL modem <---> wrt54gl <---> unmanaged gigabit switch <---> lantronix spider

My computer is connected through wrt54gl wireless.


locked by HopelessN00b Feb 18 '15 at 13:14

This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here. This question and its answers are frozen and cannot be changed. More info: help center.

closed as off-topic by HopelessN00b Feb 18 '15 at 13:14

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on Server Fault must be about managing information technology systems in a business environment. Home and end-user computing questions may be asked on Super User, and questions about development, testing and development tools may be asked on Stack Overflow." – HopelessN00b
If this question can be reworded to fit the rules in the help center, please edit the question.

up vote 4 down vote accepted

If you're trying to find the unknown, suspected static IP of the Spider, you could install Wireshark on a laptop and hook it up to the Ethernet port of the Spider. Start a capture in Wireshark and power-cycle the Spider. When the Spider boots up, it should start sending ARP requests for its default gateway, that will look something like:

Who has A.B.C.1?  Tell A.B.C.D

Where A.B.C.D will be the IP of the Spider.

Excellent suggestion - I'll try it at once. Does it need to be a cross over cable? – jaspernygaard Jul 27 '11 at 15:05
It's uncommon to require a crossover cable on newer NICs, they tend to detect the cable these days, but that of course is dependent on your equipment. – andyortlieb Jul 27 '11 at 15:17
The utility found the device, when connecting directly to the device. Next problem is that the unit is password protected and can only be reset by using the serial interface.... a cable I do not have :( – jaspernygaard Jul 27 '11 at 16:28

If you have the MAC then you could look at the CAM tables on your switches (if they have an interface to find them that is). This will not only find its IP but its physical port too.

Hmm. The current switch which the Spider is connected to is unmanaged, however the switch is connected through a wrt54gl access point. Maybe the wrt54gl will have the CAM tables? – jaspernygaard Jul 27 '11 at 15:02

I find it useful to hook up a laptop directly to the ethernet port of the device and dump all traffic as you power it on.

Usually you'll see something. If you're really lucky, it'll support IPv6 and you can hit it at the link-local address.


One of the simplest ways I've found to find the IP address of a device if you don't have console access, is to install arpwatch on either the firewall or your computer, and turn the device on. It may take a little while, but arpwatch should notice the device and either log it in /var/log/syslog, or send you an email (if you set it up that way).

If you plug it directly into a laptop or computer running arpwatch, it should find it pretty quick.


Option 1. Install wireshark on your workstation, and then plug your workstation directly (not through a switch) into the device and watch the traffic. You'll see all kinds of periodic TCP/IP traffic.

Option 2. According to the user manual (pg 4), the equipment comes with software that will discover the devices and allow you to configure them, and set their IP addresses.. My guess is that it does this with SNMP.

Yeah - the utility doesn't find anything - Maybe because I'm on the wrt54gl and the spider is on the switch – jaspernygaard Jul 27 '11 at 15:08
Did you try running the utility while plugged directly into it, or at least plugged into the same switch? – andyortlieb Jul 27 '11 at 15:18 here is a pdf on the startup guide, page 5 shows the way to help you get into it. if nothing has changed for the password then then you can get in on the default password and edit the settings to your network

I've been able to connect to the unit - see my comments to post marked as answer. Now I just need to acquire a the cable to reset the unit to factory default. Thanks for the reply. – jaspernygaard Jul 29 '11 at 7:41

As to the reset of the device, as well as anything Lantronix information related: Another option is the Lantronix DeviceInstaller application. Very nice, clean UI and can give you all the information you need about any Lantronix device on your network. It's only limitation is it won't "automatically" find devices on a different subnet. That is easily circumvented if you know the IP address by doing an "Add device" through the menu. Once connected, you can access all the information on the device as well as avoiding the need for the serial interface, do firmware upgrades, even roll back upgrades, and much more. One of the tabs connects to the device the same way you would usually have to do the (Kludgy?) serial null modem connector, press and hold the "X" key and power up the device. I use this utility constantly and it has saved me many trips to remote areas of our large campus to pickup devices to be worked on. Oh yes, you can also reset the device, but obviously once it is reset, you need to know the correct information to reconnect. The latest version can be downloaded from Lantronix DeviceInstaller page


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