You can use either LAN1 or IPMI dedicated LAN. When BMC initializes, it checks the presence of LAN connection for dedicated LAN first and then the shared (LAN1). If no cable is connected to dedicated LAN port it will check the shared LAN port and stay there. At a later stage if user decides to use dedicated LAN, then he has to do an AC power cycle or cold reset the BMC. When the user does this, the dedicated LAN cable should be connected for IPMI to use it. Else it will change back to shared LAN.

If user always wants to use a particular LAN port he can go to configuration-> LAN select and chose which ports he wants to connect. IPMI will always use this port. If no cable is connected to that port, you will not be able to connect to IPMI. Please refer to FAQ ID 9829 for more details