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3 – Planning
Multiple Chassis Fabrics
59021-05 A 3-3
3.2.2
Common Topologies
This section describes three commonly used topologies:
■ Cascade
■ Mesh
■ Multistage®
3.2.2.1
Cascade Topology
A cascade topology describes a fabric in which the switches are connected in a
linear fashion. If you connect the last switch back to the first switch, you create a
cascade-with-a-loop topology as shown in Figure 3-1. The loop reduces latency
because any switch can route traffic in the shortest direction to any switch in the
loop. The loop also provides failover should a switch fail.
The cascade fabric shown in Figure 3-1 has the following characteristics:
■ Each chassis link contributes up to 200 MB/s of bandwidth between chassis,
400 MB/s in full duplex. However, because of the sequential structure, that
bandwidth will be shared by traffic between devices on other chassis.
■ Latency between any two ports is no more than three chassis hops.
■ 48 Fibre Channel ports are available for devices.
Figure 3-1. Cascade-with-a-Loop Topology