Here is how to change the NIC for IPMI to be shared or dedicated. I know this works on SuperMicro I’m not sure about other vendors

Make sure you have IPMI tool installed and you’re able to connect via ipmitool

To Get Lan Mode

ipmitool raw 0x30 0x70 0x0C 0x00

It will return a code, here are those and their meanings:
00 dedicated
01 shared
02 Failover

Here is how you set the mode

For dedicated:

ipmitool raw 0x30 0x70 0x0C 0x01 0

For shared

ipmitool raw 0x30 0x70 0x0C 0x01 1

For failover

ipmitool raw 0x30 0x70 0x0C 0x01 2