Redundency sim

Hello there,

I am working on Nexcom MVS-5600 and i am using Openwrt in WWAN1 module it supports 2 sim cards but one of them is active and the other is idle which will be activate it once the active gets disconnected.
How can i make the logic of reduandency between this 2 sims work? As i can get the ip of the active one but when i put the sim in the idle its not being detected.

Thank you in advance

Check Automatic SIM switching