Local LAN, Ubuntu laptop and Viasat Surfbeam SM2101 modem are connected to the router, wired connection. I can't find an internal IP address of satmodem connected to the router. Router only show laptop connected. I tried scan network range 192.168.1.0 - 192.168.1.255 use angry ip scanner, nmap, but they does not show satmodem. I'm not sure does it have DHCP enabled or not, there is no reset button. I tried also directly connect ethernet port of satmodem to the laptop and scan with ip scanner, also use nmap -sP 192.168.1.0/24, but it does not show it. The Network LED indicator on the modem is light means it working. I have no manual on that device, but in the configuration Guide for old version of satmodem was specified that during modem configuration, the "Support PC’s Operating System" should be configured for a static IP address of 192.168.1.2. Not sure that that's the case, as such configuration was used in quite old hardware.
Please update your question with the exact brand and model of the Satmodem.
tcpdump -i eth0 (or Wireshark) on laptop, connect satmodem directly to laptop, see if it broadcasts anything (like a DHCP request).
2) You probably did that, but when scanning for IPs, make sure you have the correct address and netmask statically assigned to
eth0 (check with
ip addr), and no other program tries (e.g. network manager) tries to interfere with that.
3) Connect satmodem directly to laptop, statically assign each of the complete private network ranges to it, scan complete range. Start with
4) Sometimes embedded devices behave differently directly after startup when the boot loader is running, e.g. they may react to different static IPs etc. Or there may be special modes you can get into by pressing the power switch for a longer time etc. This might provide an angle.