Cisco Nexus 5000 Series Switch Fabric Manager Software Configuration Guide, NX-OS 4.0 (OL-16598-01, June 2008)

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Nexus 5000 Series Switch Fabric Manager Software Configuration Guide
OL-16598-01
Chapter 18 Configuring Fibre Channel Routing Services and Protocols
Information About FSPF
• Uses a topology database to keep track of the state of the links on all switches in the fabric and
associates a cost with each link.
• Guarantees a fast reconvergence time in case of a topology change. Uses the standard Dijkstra
algorithm, but there is a static dynamic option for a more robust, efficient, and incremental Dijkstra
algorithm. The reconvergence time is fast and efficient as the route computation is done on a per
VSAN basis.
FSPF Examples
This section provides examples of topologies and applications that demonstrate the benefits of FSPF.
Note The FSPF feature can be used on any topology.
Fault Tolerant Fabric Example
Figure 18-1 depicts a fault tolerant fabric using a partial mesh topology. If a link goes down anywhere
in the fabric, any switch can still communicate with all others in the fabric. In the same way, if any switch
goes down, the connectivity of the rest of the fabric is preserved.
Figure 18-1 Fault Tolerant Fabric
For example, if all links are of equal speed, the FSPF calculates two equal paths from A to C: A-D-C
(green) and A-E-C (blue).
Redundant Link Example
To improve on the topology in Figure 18-1, each connection between any pair of switches can be
replicated; two or more links can be present between a pair of switches. Figure 18-2 shows this
arrangement. Because switches in the Nexus 5000 Series support port channels, each pair of physical
links can appear to the FSPF protocol as one single logical link.
By bundling pairs of physical links, FSPF efficiency is considerably improved by the reduced database
size and the frequency of link updates. Once physical links are aggregated, failures are not attached to a
single link but to the entire SAN port channel. This configuration also improves the resiliency of the
network. The failure of a link in a SAN port channel does not trigger a route change, which reduces the
risks of routing loops, traffic loss, or fabric downtime for route reconfiguration.
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