3.4 Topologies

There will be more information about hubs and specifically Hewlett-Packard hubs in Chapter 5. However, for now, to demonstrate a couple of topologies using hubs see Figures 3-9 and 3-10.

Figure 3-9. Cascaded Shortwave Hub Topology

Figure 3-10. Cascaded Long-wave Hub Topology

3.4.1 Cascading Shortwave Hubs

A server with an FC-AL, short-wave host bus adapter (HBA) can connect to an FC-AL hub 500 meters away. Each of the 10 ports on the hub can connect to an FC-AL device up to 500 meters away.

Cascaded hubs use one port on each hub for the hub-to-hub connection and this increases the potential distance between nodes in the loop an additional 500 meters. In this topology the overall distance is 1500m. Both hubs can support other FC-AL devices at their physical locations. Stated distances assume a 50 micron multimode cable.

3.4.2 Cascading Long-wave Hubs

Cascaded FC-AL, non-OFC, long-wave hubs use the long-wave port for the hub-to-hub connection. Ports 1 through 9 on each long-wave hub are for connections to FC-AL devices. When cascading long-wave hubs, only use the long-wave port on each hub to connect the hubs. The overall distance in this topology is 11,000 meters. There is 500m from the server to the first hub, plus 10,000m between the two long-wave hubs, plus 500m from the second hub to the final device.