Hello,
Thank you for your Query,
Teltonika devices support Bridge mode, but it can be restrictive in terms of how it functions, and it may require setting up a static IP for devices connected to it to reach the router. How to set up bridge mode can be found here Mobile Bridge mode troubleshooting - Teltonika Networks Wiki (teltonika-networks.com).
The better alternative is the passthrough mode and you will start by ensuring no failover is enabled, Secondly, ensure that the LAN has DHCP enabled, thirdly, navigate to Network → Interfaces → Interfaces: MOB1S1A1 and choose passthrough through mode where you will use the mac address of the device that the IP is to be assigned and finally you will have to reboot the TRB500 for changed to take effect. With these settings, you will still be able to utilize SMS utilities.
Lastly, could you please give more information on how you would want to utilize VLAN in the Mobile interface? I am attaching a page that will guide you on where to set up an interface-based VLAN in Teltonika devices as one of the VLANs that our devices support. RUTX11 VLAN - Teltonika Networks Wiki
Best regards,
Kennedy. K