A method, apparatus, and computer-readable media for a stackable
multi-layer switch comprises a first set of stack units comprising a
master stack unit, wherein one of the stack units in the first set
comprises a first port to communicate with a network using a first
Internet Protocol address; and a second set of the stack units comprising
a backup master stack unit, wherein one of the stack units in the second
set comprises a second port to communicate with the network using the
first Internet Protocol address; wherein each of the stack units
comprises a control plane processor, one or more ports, a stacking
interface, and a forwarding engine to communicate with the control plane
processor, the ports, and the stacking interface; wherein the stack units
communicate with each other through the stacking interfaces; and wherein,
when the master stack unit is unable to communicate with the backup
master stack unit through the stacking interfaces, the first and second
ports attempt to communicate with each other over the network using a
second Internet Protocol address associated with the first port and a
third Internet Protocol address associated with the second port.