What dual sim mode is Redmi Note 4 having?

Redmi Note 4 supports dual Standby mode. The 2 SIM cards are active when none of them are in used. But when one is on a call, the other one will be inactive.

If you wish to get alerts of calls from either one of the SIM cards when either one is engaged, you’ll need to enable call waiting for both SIM cards and set the call forwarding in this way:

1. When SIM 2 is unreachable (inactive when SIM 1 is on a call), forward to SIM 1 number.
2. When SIM 1 is unreachable (inactive when SIM 2 is on a call), forward it to SIM 2 number.