If possible, the designer can include some unused ports in a hardware zone. So, in the event of a particular port failing, maybe caused by a GBIC or transceiver problem, the cable could be moved to a different port in the same zone. This would mean that the zone would not need to be reconfigured. 3.8.2 Software zoning Software zoning is implemented by the fabric operating systems within the fabric switches. When using software zoning the members of the zone can be defined using their World Wide Names: Node WWN Port WWN Usually, zoning software also allows you to create symbolic names for the zone members and for the zones themselves. Dealing with the symbolic name or aliases for a device is often easier than trying to use the WWN address. The number of members possible in a zone is limited only by the amount of memory in the fabric switch. A member can belong to multiple zones. You can define multiple sets of zones for the fabric, but only one set can be active at any time. You can activate another zone set any time you want, without the need to power down the switch. With software zoning there is no need to worry about the physical connections to the switch. If you use WWNs for the zone members, even when a device is connected to another physical port, it will still remain in the same zoning definition, because the device's WWN remains the same. The zone follows the WWN. Important: However, by stating this, it does not automatically mean that if you unplug a device, such as a disk subsystem, and plug it into another switch port, that your host will still be able to communicate with your disks (until you either reboot or unload and load your operating system device definitions), even if the device remains member of that particular zone. This depends on components you use in your environment, like operating system and multipath software. Shown in Figure 3-34 on page 102 is an example of WWN-based zoning. In this example, symbolic names are defined for each WWN in the SAN to implement the same zoning requirements, as shown in the previous Figure 3-32 on page 99 for port zoning: Zone_1 contains the aliases alex, ben, and sam, and is restricted to only these devices. Chapter 3. SAN features 101