> # Information About FSPF

> Fabric Shortest Path First (FSPF) is the standard path selection protocol used by Fibre Channel fabrics. The FSPF feature is enabled by default on all Fibre Channel switches. Except in configurations that require special consideration, you do not need to configure any FSPF services. FSPF automatically calculates the best path between any two switches in a fabric. FSPF provides these features:

> - Dynamically compute routes throughout a fabric by establishing the shortest and quickest path between any two switches.
> - Select an alternative path in the event of the failure of a given path. FSPF supports multiple paths and automatically computes an alternative path around a failed link. It provides a preferred route when two equal paths are available.

> FSPF is the protocol currently standardized by the T11 committee for routing in Fibre Channel networks. The FSPF protocol has the following characteristics and features:

> - Supports multipath routing.
> - Bases path status on a link state protocol.
> - Routes hop by hop, based only on the domain ID.
> - Runs only on E ports or TE ports and provides a loop free topology.
> - Runs on a per VSAN basis. Connectivity in a given VSAN in a fabric is guaranteed only for the switches configured in that VSAN.
> - 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.

> This section includes the following topics:

> - FSPF Global Configuration
> - About SPF Computational Hold Times
> - About Link State Record Defaults
> - About FSPF Link Cost
> - About Hello Time Intervals
> - About Dead Time Intervals
> - About Retransmitting Intervals
> - About Disabling FSPF for Specific Interfaces
> - FSPF Routes
> - About Fibre Channel Routes
> - About Broadcast and Multicast Routing
> - About Multicast Root Switch
> - In-Order Delivery
> - About Reordering Network Frames
> - About Reordering PortChannel Frames
> - About Enabling In-Order Delivery
> - About Flow Statistics

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