Hi,
The mobile interfaces represent sim slots, MOB1S1A1 interface is for the SIM in SIM slot 1, while MOB1S2A1 is for SIM in slot 2. However, since RUT950 has only one mobile module - only one mobile interface can be active at one time, either MOB1S1A1 or MOB1S2A1.
Usually, when you configure SIM switching or failover for mobile interfaces, and the devices lose connection on one of the SIM cards, the devices swap to the other SIM card. Hence, if you lose connection on SIM1, the MOB1S1A1 interface goes down and the MOB1S2A1 interface is activated for SIM2.
Currently, RUTX12 is the only Teltonika device that has 2 separate mobile modules. This means that RUTX12 can have both mobile interfaces active at the same time. Hence, both MOB1S1A1 and MOB1S2A1 interfaces are active simultaneously.
When it comes to LTE speed, there are many variables, such as weak signal strength, slow frequency bands, overloaded tower, and others. These affect connection stability as well.
RUT950 has an LTE CAT4 module. This means download speeds of up to 150 Mbps and upload of up to 50Mbps. However, these are the maximum speeds, meaning that in real environments the speeds are way less.
You can connect to the device via webUI and navigate to Status -> Network -> Mobile. You will see information regarding signal strength, LTE band, RSRP, and other parameters. You can then refer to the information available HERE to see if your mobile connection is good.
Also, take a look at THIS page. It explains why some devices have different speeds.
Kind Regards,
Andzej