Configuring Two-unit Stack Linear-topology Trunks
FastIron 08.0.90 and later releases support a linear-topology trunk in a two-unit stack. A two-unit stack can form a linear-topology trunk containing all stacking ports, instead of dividing the ports into the two directions of a ring topology. The linear-topology trunk provides the same redundancy as a two-unit ring because of trunk load balancing. Furthermore, a linear-topology trunk doubles the bandwidth of the stacking ports between two units.
In a two-unit ring topology, only one direction is used even though there are two paths for a unit to reach the other unit. In contrast, a linear-topology trunk uses all ports to reach the other unit.