Dell PowerVault 50F (Fibre Channel Switch) - Manual (Page 19)

PowerVault™ 50F Topologies: Dell™ PowerVault™ 50F 8-Port Fibre Channel Switch Installation and Troubleshooting Guide
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Regardless of the topology used, the switch's extremely low message latency minimizes Fabric message
handling time that results in a high-performance Fabric.
Routing Cost
All Inter Switch Links (ISLs) have a default cost of 1000. The cost of a path between any two switches in the
Fabric is the sum of the costs of all ISLs. The switches that comprise the Fabric always choose the lowest
cost path through the Fabric to forward frames from the source switch to the destination switch.
When constructing a multiswitch configuration, called a cascaded Fabric, a frame entering the Fabric may
pass through eight switches before exiting the Fabric. The switch does not enforce the eight-switch limit. It is
your responsibility to ensure that the seven-hop limit is not exceeded. The command uRouteShow provides
information regarding the cost of the shortest path to another switch from which you can derive the number
of hops. The cost should not exceed 7000 (7 x 1000).
A Fabric using Dell switches in cascaded topologies should be configured to deliver the required bandwidth
and fault tolerance with all connections made within the seven-hop maximum limit.
Configuring Switches
When configuring switches in a Fabric, optimize the Fabric performance based on the most significant
expected use.
NOTE: Except for unique identifiers such as the switch name, domain name, and IP address, all switches in a Fabric must
have the same firmware configuration. Switches that are configured differently are isolated from the Fabric.
Cascaded topologies using multiple switches give switching system designers a powerful, flexible set of
resources to create high-performance, robust storage area networks (SAN), or data center backbone.
Loop Support
The FL_Port interface card enables any Fabric-connected device to communicate with public or private fibre
channel disks or other device types.
NOTE: Loops may contain any combination of public or private loop devices.
Public Operation
In public operation, all loop devices are accessible to all other Fabric-connected devices and loop devices
within the Fabric. The loop devices behave the same as devices attached directly to the Fabric.
Private Operation
Dell's FL_Port translative mode allows private devices on a local loop to communicate with Fabric-attached
devices and vice versa. Fabric-attached devices can be either N_Ports attached to G_Ports or public
NL_Ports attached to other FL_Ports.
Logically, private and Fabric-attached devices that communicate to a loop appear to be devices on the same
loop as the private devices. Each Fabric-attached device uses an unassigned AL_PA from the local loop.
When private devices on a local loop and Fabric-attached devices communicate, the FL_Port automatically