Vixel 9000 Series Installation & Configuration Guide CHAPTER 4 Using Fabric Services
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Routing in the Switch
The switch establishes paths to other switches using the FSPF (Fabric Shortest Path
First) routing protocol.
Packets exchanged between devices are first passed to the local switch (the switch
directly connected to the originating device). If the destination device is on the same
switch, the local switch delivers the packets to the designated Area and Port. If the
destination device is on another switch, the local switch routes the packets via FSPF
to the destination switch, which then delivers the packets to the destination device
(at the designated Area and Port). This routing operation is invisible to the origi-
nating device.
SNS commands from host bus adapters (HBAs) and other devices are echoed across
all switches in the fabric.
The switch keeps track of directly connected devices in the SNS Table; paths to
connected switches are listed in the FSPF Routing Table.
Multi-switch Topologies
In addition to the star (single-level cascade) topology supported in Stealth-3 Mode,
Fabric and Fabric (Public/Private) Modes also support mesh topologies. While a
cascade topology consists of a root switch and one or more cascade levels of
connected switches, a mesh topology consists of a web of inter-switch links (ISLs);
each switch is connected to all other switches, which makes the topology fault-
tolerant and multiple-path redundant. Switches in mesh topologies use the shortest
available path; if an ISL stops functioning, the source switch uses the next quickest
path. To create failover redundancy in cascade topologies, use multiple ISLs
between switches.
Note: The Vixel 9000
Series Switch’s high hop
allowance gives you the
freedom to size your
topology as needed. The
Vixel 9000 Series Switch is
designed for 15 linear hops
and tested up to 7 hops.
Each hop is a switch that
the source switch can
communicate through to
and including the
destination switch. If
multiple paths are
available, the switch uses
the shortest path.
Maximum switch quantities for each topology are listed below.
• Star (single-level cascade) topology, per root switch: 16 cascaded switches for
Vixel 9200; 8 cascaded switches for Vixel 9100.
• Mesh topology, per switch: 16 inter-switch links for Vixel 9200; 8 inter-switch
links for Vixel 9100.
Domain numbers for each connected switch (in Fabric Mode or Fabric (Public/
Private) Mode) are assigned by the “principal switch.” The “principal switch”
designation is given to the switch with the lowest World-wide Name (WWN).
To view the “principal switch” status and domain ID for a switch, in the Command
Line Interface (CLI) type show system from the Root Menu; in the Web
Manager click System from the available options.
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General