Thank you for contacting.
Could you please check on top right corner or webui what firmware are you using ?
Have you tried upgrading to the latest ?
Its highly recommended to upgrade.
For the modem access its working fine. Now if you want to access the server from modem(Outside server network) there are no configurations for that on Rutxx device. All configurations will be done on the Linux server side.
If you want to access the linux server that is connected to the Rutxx modem from any remote location . You need to do a simple port forwarding .If it supports ssh or http protocol.
Same could also be done with RMS:
Its supporting VNC,RDP, HTTP(S) and SSH protocols. VNC is a protocol supported by Linux.
It would be better if you provide me with more details:
Like both devices are on same network or different ?
How everything is connected in case to access the linux machine from Teltonika router ?
What are ports and IP's on both the devices ?
Can you draw a network topology for your scenario for my understandings ?