You can use ipmitool CLI (command line interface) to change it, there is SMT and AMI format . Please email to support@supermicro.com for more information.

Example of CLI :
Ipmitool –H 172.31.1.11 –U ADMIN –P ADMIN raw 0x30 0x70 0x0C 1 0


// for ATEN
LAN mode get:
Input : NetFn 0x30
Cmd 0x70
Param1 0x0c
Param2 0 [read]

Output: Completion Code 0x00
Data [dedicated/onBoard/failover]

LAN mode set:
Input : NetFn 0x30
Cmd 0x70
Param1 0x0c
Param2 1 [write]
Param3 [dedicated/onBoard/failover]

Output: Completion Code 0x00
dedicated: 0
onBoard: 1
failover: 2

// for AMI
LAN mode get:
Input : NetFn 0x30
Cmd 0x70
Param1 0x0c
Param2 0 [read]
Param3 [disable/enable] -> 0/1

Output: Completion Code 0x00
Data [dedicated/onBoard]

LAN mode set:
Input : NetFn 0x30
Cmd 0x70
Param1 0x0c
Param2 1 [write]
Param3 [disable/enable]
Param4 [dedicated/onBoard] -> 0/1

Output: Completion Code 0x00
dedicated: 0
onBoard: 1