Issue Description
Two S12704 set up CSS and work well and ACU2 board install on slot 2 of each S12704. 
But when customer want to login ACU2 board on slave chassis, there is no identifier for it.
Customer login the master S12704 first, then login the ACU2 board with command connect slot 1/2, login ACU2 board successful.
But when customer want to login ACU2 board on slave chassis, there is no identifier for it.
Alarm InformationNA
Handling Process1. Checking the state of the ACU2 board, both of the board are normal.
2. Checking the CSS state, it is normal.
Root CauseThe root cause of the issue is that ACU2 board on slave chassis cannot login from master chassis with command connect slot .
SolutionOn the master chassis, use the following command to login the slave chassis first and then login the ACU2 board on slave chassis.
<Huawei> local-telnet slave
