50 Chapter 2 Network configuration209418-ABase unitThe base unit is the unique stack unit that you configure with the Unit Selectswitch on the front panel. One BayStack 420 Switch in the stack must beconfigured as the base unit; all other units in the stack must have their Unit Selectswitch set to Off (see “Unit select switch” on page 49). You can assign any singleBayStack 420 Switch as the base unit.The physical ordering of all of the other units in the stack is determined by theposition of the base unit within the stack. This is important for networkmanagement applications that view the physical ordering of the units within thestack.Some characteristics of the base unit are described in the following sections.Initial installationDuring the initial installation of the stack, the software automatically determinesthe physical order of all units in the stack according to the position of the base unitwithin the stack. Thereafter, the individual units maintain their original unitnumbering, even if you change the position of one or more units in the stack (youcan renumber the units using the Renumber Stack Units screen; see “RenumberStack Units screen” on page 154).For example, when you initially power up the stack, the base unit becomes unit 1and the unit that the base unit connects to becomes unit 2 (and the next unit is unit3 and so on), until the maximum stack configuration (up to 8 units) is reached. Ifyou change the base unit to another unit in the stack, the new base unit keeps itsoriginal unit number in the stack.Stack MAC addressWhen the switch is participating in a stack configuration, a stack MAC address isautomatically assigned during the stack initialization. The base unit’s MACaddress, with a software offset, is used for the stack MAC address.For example, if the base unit’s MAC address is 00-00-82-99-44-00, and the stacksoftware offset is 1F, then the stack MAC address becomes:00-00-82-99-44-1F
