- Preface
- Product Overview
- Installing Cisco Fabric Manager
- Fabric Manager Server
- Authentication in Fabric Manager
- Fabric Manager Client
- Device Manager
- Using Cisco Fabric Services
- Configuring Ethernet Interfaces
- Configuring Virtual Interfaces
- Configuring Fibre Channel Interfaces
- Configuring N-Port Virtualization
- Configuring Domain Parameters
- Configuring VSAN Trunking
- Configuring and Managing VSANs
- Configuring and Managing Zones
- Distributing Device Alias Services
- Configuring Fibre Channel Routing Services and Protocols
- Managing FLOGI, Name Server, FDMI, and RSCN Databases
- Configuring SPAN
- Discovering SCSI Targets
- Configuring SAN PortChannels
- Advanced Features and Concepts
- Configuring FC-SP and DHCHAP
- Configuring Port Security
- Configuring Fabric Binding
- Configuring Fabric Configuration Servers
- Configuring Port Tracking
- Network Monitoring
- Performance Manager
- Nexus 5000 Management Software FAQ
- Troubleshooting Your Fabric
- Index
- About FSPF Link Cost
- Configuring FSPF Link Cost
- About Hello Time Intervals
- Configuring Hello Time Intervals
- About Dead Time Intervals
- Configuring Dead Time Intervals
- About Retransmitting Intervals
- Configuring Retransmitting Intervals
- About Disabling FSPF for Specific Interfaces
- Disabling FSPF for Specific Interfaces
- Displaying the FSPF Database
- Viewing FSPF Statistics
Configuring Fibre Channel Routing Services and Protocols
Fabric Shortest Path First (FSPF) is the standard path selection protocol used by Fibre Channel fabrics. The FSPF feature is enabled by default on the E mode and TE mode Fibre Channel interfaces on Cisco Nexus 5000 Series 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 the following capabilities:
•
Dynamically computes routes throughout a fabric by establishing the shortest and quickest path between any two switches.
•Selects 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.
This chapter provides details on Fibre Channel routing services and protocols. It includes the following sections:
Information About FSPF
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.
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 Cisco 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.
Figure 18-2 Fault Tolerant Fabric with Redundant Links
For example, if all links are of equal speed and no SAN port channels exist, the FSPF calculates four equal paths from A to C: A1-E-C, A2-E-C, A3-D-C, and A4-D-C. If SAN port channels exist, these paths are reduced to two.
FSPF Global Configuration
By default, FSPF is enabled on switches in the Cisco Nexus 5000 Series.
Some FSPF features can be globally configured in each VSAN. By configuring a feature for the entire VSAN, you do not have to specify the VSAN number for every command. This global configuration feature also reduces the chance of typing errors or other minor configuration errors.
Note FSPF is enabled by default. Generally, you do not need to configure these advanced features.
The default for the backbone region is 0 (zero). You do not need to change this setting unless your region is different from the default. If you are operating with other vendors using the backbone region, you can change this default to be compatible with those settings.
This section includes the following topics:
•About SPF Computational Hold Times
•Resetting FSPF to the Default Configuration
About SPF Computational Hold Times
The SPF computational hold time sets the minimum time between two consecutive SPF computations on the VSAN. Setting this to a small value means that FSPF reacts faster to any fabric changes by recomputing paths on the VSAN. A small SPF computational hold time uses more switch CPU time.
About Link State Records
Each time a new switch enters the fabric, a link state record (LSR) is sent to the neighboring switches, and then flooded throughout the fabric.
Table 18-1 displays the default settings for switch responses.
The LSR minimum arrival time is the period between receiving LSR updates on this VSAN. Any LSR updates that arrive before the LSR minimum arrival time are discarded.
The LSR minimum interval time is the frequency at which this switch sends LSR updates on a VSAN.
Configuring FSPF on a VSAN
To configure an FSPF feature for the entire VSAN using Fabric Manager, perform this task:
Step 1 Expand a Fabric, expand a VSAN, and then choose FSPF for a VSAN that you want to configure for FSPF.
You see the FSPF configuration in the Information pane as shown in Figure 18-3.
Figure 18-3 FSPF General Information
You can enter values for RegionID, Spf Comp Holdtime, LSR Min Arrival, and LSR Min Interval. These values apply to all interfaces on the VSAN.
Step 2 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
Resetting FSPF to the Default Configuration
To return the FSPF VSAN global configuration to its factory default using Fabric Manager, perform this task:
Step 1 Expand a Fabric, expand a VSAN and then choose FSPF for a VSAN that you want to configure for FSPF.
You see the FSPF configuration in the Information pane as shown in Figure 18-3.
Step 2 Check the SetToDefault check box for a switch.
Step 3 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
Enabling or Disabling FSPF
To enable or disable FSPF using Fabric Manager, perform this task:
Step 1 Expand a Fabric, expand a VSAN, and then choose FSPF for a VSAN that you want to configure for FSPF.
You see the FSPF configuration in the Information pane as shown in Figure 18-3.
Step 2 Set the Status Admin drop-down list to up to enable FSPF or to down to disable FSPF.
Step 3 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
FSPF Interface Configuration
Several FSPF commands are available on a per-interface basis. These configuration procedures apply to an interface in a specific VSAN.
This section includes the following topics:
•Configuring Hello Time Intervals
•Configuring Dead Time Intervals
•About Retransmitting Intervals
•Configuring Retransmitting Intervals
•About Disabling FSPF for Specific Interfaces
•Disabling FSPF for Specific Interfaces
About FSPF Link Cost
FSPF tracks the state of links on all switches in the fabric, associates a cost with each link in its database, and then chooses the path with a minimal cost. The cost associated with an interface can be administratively changed to implement the FSPF route selection. The integer value to specify cost can range from 1 to 65,535. The default cost for 1 Gbps is 1000 and for 2 Gbps is 500.
Configuring FSPF Link Cost
To configure FSPF link cost using Fabric Manager, perform this task:
Step 1 In the Physical Attributes pane, expand Switches > Interfaces, and then choose FC Physical.
You see the interface configuration in the Information pane.
Step 2 Click the FSPF tab.
You see the FSPF interface configuration in the Information pane as shown in Figure 18-4.
Figure 18-4 Fibre Channel Physical FSPF Interface
Step 3 Double-click in the Cost field of a switch and change the value.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
About Hello Time Intervals
You can set the FSPF Hello time interval to specify the interval between the periodic hello messages sent to verify the health of the link. The integer value can range from 1 to 65,535 seconds.
Note This value must be the same in the ports at both ends of the ISL.
Configuring Hello Time Intervals
To configure the FSPF Hello time interval using Fabric Manager, perform this task:
Step 1 In the Physical Attributes pane, expand Switches > Interfaces, and then choose FC Physical.
You see the interface configuration in the Information pane.
Step 2 Click the FSPF tab.
You see the FSPF interface configuration in the Information pane as shown in Figure 18-4.
Step 3 Change the Hello Interval field for a switch.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
About Dead Time Intervals
You can set the FSPF dead time interval to specify the maximum interval for which a hello message must be received before the neighbor is considered lost and removed from the database. The integer value can range from 1 to 65,535 seconds.
Note This value must be the same in the ports at both ends of the ISL.
Configuring Dead Time Intervals
To configure the FSPF dead time interval using Fabric Manager, perform this task:
Step 1 In the Physical Attributes pane, expand Switches > Interfaces, and then choose FC Physical.
You see the interface configuration in the Information pane.
Step 2 Click the FSPF tab.
You see the FSPF interface configuration in the Information pane as shown in Figure 18-4.
Step 3 Double-click the Dead Interval field for a switch and provide a new value.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
About Retransmitting Intervals
You can specify the time after which an unacknowledged link state update should be transmitted on the interface. The integer value to specify retransmit intervals can range from 1 to 65,535 seconds.
Note This value must be the same on the switches on both ends of the interface.
Configuring Retransmitting Intervals
To configure the FSPF retransmit time interval using Fabric Manager, perform this task:
Step 1 In the Physical Attributes pane, expand Switches > Interfaces, and then choose FC Physical.
You see the interface configuration in the Information pane.
Step 2 Click the FSPF tab.
You see the FSPF interface configuration in the Information pane as shown in Figure 18-4.
Step 3 Double-click the ReTx Interval field and enter a value.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
About Disabling FSPF for Specific Interfaces
You can disable the FSPF protocol for selected interfaces. By default, FSPF is enabled on all E ports and TE ports. This default can be disabled by setting the interface as passive.
Note FSPF must be enabled at both ends of the interface for the protocol to work.
Disabling FSPF for Specific Interfaces
You can disable the FSPF protocol for selected interfaces. By default, FSPF is enabled on all E ports and TE ports. This default can be disabled by setting the interface as passive.
To disable FSPF for a specific interface using Fabric Manager, perform this task:
Step 1 In the Physical Attributes pane, expand Switches > Interfaces, and then choose FC Physical.
You see the interface configuration in the Information pane.
Step 2 Click the FSPF tab.
You see the FSPF interface configuration in the Information pane as shown in Figure 18-4.
Step 3 In the Admin Status drop-down list, choose down.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
You can disable the FSPF protocol for selected interfaces. By default, FSPF is enabled on all E ports and TE ports. This default can be disabled by setting the interface as passive.
Displaying the FSPF Database
The FSPF database for a specified VSAN includes the following information:
•Link State Record (LSR) type
•Domain ID of the LSR owner
•Domain ID of the advertising router
•LSR age
•LSR incarnation member
•Number of links
To display the FSPF database using Device Manager, perform this task:
Step 1 Choose FC > Advanced > FSPF.
You see the FSPF dialog box as shown in Figure 18-5.
Figure 18-5 FSPF Dialog Box in Device Manager
Step 2 Click the LSDB LSRs tab.
You see the FSPF database information as shown in Figure 18-6.
Figure 18-6 FSPF Database Information in the LSDB LSRs Tab
Step 3 Click Close to close the dialog box.
Viewing FSPF Statistics
To view FSPF statistics using Fabric Manager, perform this task:
Step 1 Expand a Fabric, expand a VSAN, and then choose FSPF in the Logical Domains pane.
You see the FSPF configuration dialog box.
Step 2 Click the Statistics tab.
You see the FSPF VSAN statistics in the Information pane as shown in Figure 18-7.
Figure 18-7 FSPF VSAN Statistics
Step 3 Click the Interface Statistics tab.
You see the FSPF interface statistics in the Information pane.
FSPF Routes
FSPF routes traffic across the fabric, based on entries in the FSPF database. These routes can be learned dynamically, or configured statically.
This section includes the following topics:
•Configuring Fibre Channel Routes
About Fibre Channel Routes
Each port implements forwarding logic, which forwards frames based on its FC ID. Using the FC ID for the specified interface and domain, you can configure the specified route (for example, FC ID 111211 and domain ID 3) in the switch with domain ID 1 (see Figure 18-8).
Figure 18-8 Fibre Channel Routes
Configuring Fibre Channel Routes
If you disable FSPF, you can manually configure a Fibre Channel route. To configure a Fibre Channel route using Device Manager, perform this task:
Step 1 Click FC > Advanced > Routes.
You see the FC Static Route Configuration dialog box as shown in Figure 18-9.
Figure 18-9 Fibre Channel Static Route Configuration Dialog Box
Step 2 Click Create to create a static route.
You see the Create Route dialog box as shown in Figure 18-10.
Figure 18-10 Create Fibre Channel Route Dialog Box
Step 3 Choose the VSAN ID that for which you are configuring this route.
Step 4 Fill in the destination address and destination mask for the device you are configuring a route.
Step 5 Choose the interface that you want to use to reach this destination.
Step 6 Choose the next hop domain ID and route metric.
Step 7 Check either the local or remote radio button.
Step 8 Click Create to save these changes, or click Close to discard any unsaved changes.
In-Order Delivery
In-order delivery (IOD) of data frames guarantees frame delivery to a destination in the same order that they were sent by the originator.
Some Fibre Channel protocols or applications cannot handle out-of-order frame delivery. In these cases, switches in the Cisco Nexus 5000 Series preserve frame ordering in the frame flow. The source ID (SID), destination ID (DID), and optionally the originator exchange ID (OX ID) identify the flow of the frame.
On a switch with IOD enabled, all frames received by a specific ingress port and destined to a certain egress port are always delivered in the same order in which they were received.
Use IOD only if your environment cannot support out-of-order frame delivery.
Tip If you enable the in-order delivery feature, the graceful shutdown feature is not implemented.
This section includes the following topics:
•About Reordering Network Frames
•About Reordering SAN Port Channel Frames
•About Enabling In-Order Delivery
•Enabling In-Order Delivery Globally
•Enabling In-Order Delivery for a VSAN
•Configuring the Drop Latency Time
About Reordering Network Frames
When you experience a route change in the network, the new selected path may be faster or less congested than the old route.
Figure 18-11 Route Change Delivery
In Figure 18-11, the new path from Switch 1 to Switch 4 is faster. In this scenario, Frame 3 and Frame 4 may be delivered before Frame 1 and Frame 2.
If the in-order guarantee feature is enabled, the frames within the network are delivered as follows:
•Frames in the network are delivered in the order in which they are transmitted.
•Frames that cannot be delivered in order within the network latency drop period are dropped inside the network.
About Reordering SAN Port Channel Frames
When a link change occurs in a SAN port channel, the frames for the same exchange or the same flow can switch from one path to another faster path.
Figure 18-12 Link Congestion Delivery
In Figure 18-12, the port of the old path (red dot) is congested. In this scenario, Frame 3 and Frame 4 can be delivered before Frame 1 and Frame 2.
When the in-order delivery feature is enabled and a port channel link change occurs, the frames crossing the SAN port channel are delivered as follows:
•Frames using the old path are delivered before new frames are accepted.
•The new frames are delivered through the new path after the network latency drop period has elapsed and all old frames are flushed.
Frames that cannot be delivered in order through the old path within the network latency drop period are dropped. See the "Configuring the Drop Latency Time" section.
About Enabling In-Order Delivery
You can enable the in-order delivery feature for a specific VSAN or for the entire switch. By default, in-order delivery is disabled on switches in the Cisco Nexus 5000 Series.
Tip We recommend that you only enable this feature when devices that cannot handle any out-of-order frames are present in the switch. Load-balancing algorithms within the Cisco Nexus 5000 Series switch ensure that frames are delivered in order during normal fabric operation. The load-balancing algorithms based on source FC ID, destination FC ID, and exchange ID are enforced in hardware without any performance degradation. However, if the fabric encounters a failure and the in-order delivery feature is enabled, the recovery will be delayed because of an intentional pausing of fabric forwarding to purge the fabric of resident frames that could potentially be forwarded out-of-order.
Enabling In-Order Delivery Globally
To ensure that the in-order delivery parameters are uniform across all VSANs on the switch, enable in-order delivery globally.
Only enable in-order delivery globally if this is a requirement across your entire fabric. Otherwise, enable IOD only for the VSANs that require this feature.
Enabling In-Order Delivery for a VSAN
When you create a VSAN, that VSAN automatically inherits the global in-order guarantee value. You can override this global value by enabling or disabling in-order guarantee for the new VSAN.
To use the lowest domain switch for the multicast tree computation using Fabric Manager, perform this task:
Step 1 Expand a fabric and then choose All VSANS.
Step 2 Click the Attributes tab.
You see the general VSAN attributes in the Information pane as shown in Figure 18-13.
Figure 18-13 General VSAN Attributes
Step 3 Check the InOrder Delivery check box to enable IOD for the switch.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
Configuring the Drop Latency Time
You can change the default latency time for either the entire switch or a specified VSAN in a switch.
To configure the drop latency time for a switch using Fabric Manager, perform this task:
Step 1 Expand a fabric and then choose All VSANS.
You see the VSAN configuration in the Information pane.
Step 2 Click the Attributes tab.
You see the general VSAN attributes in the Information pane as shown in Figure 18-14.
Figure 18-14 General VSAN Attributes
Step 3 Double-click the Network Latency field and change the value.
Step 4 Click Apply Changes to save these changes, or click Undo Changes to discard any unsaved changes.
Default Settings
Table 18-2 lists the default settings for FSPF features.
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