I wrote a program for finding all of the Lantronix devices on the network:

jjeffers@solar:~/lantronix$ findLantronix
# The following Lantronix devices are on the local network:
192.168.10.232  00:20:4A:A8:49:F3
jjeffers@solar:~/lantronix$

Below is the code, if you want to play with it. Basically the Lantronix will send a reply if it gets a special UDP packet on port 30718. Then you can see what IP replied, firmware version, and MAC address.

-James Jefferson Jarvis
APRS World, LLC
+1-507-454-2727
www.aprsworld.com