Cisco Nexus 5000 Series NX-OS Software Configuration Guide
Configuring Port Tracking
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Configuring Port Tracking

Table Of Contents

Configuring Port Tracking

Information About Port Tracking

Configuring Port Tracking

Enabling Port Tracking

About Configuring Linked Ports

Operationally Binding a Tracked Port

About Tracking Multiple Ports

Tracking Multiple Ports

About Monitoring Ports in a VSAN

Monitoring Ports in a VSAN

About Forceful Shutdown

Forcefully Shutting Down a Tracked Port

Displaying Port Tracking Information

Default Port Tracking Settings


Configuring Port Tracking


Cisco Nexus 5000 Series switches offer the port tracking feature on physical Fibre Channel interfaces (but not on virtual Fibre Channel interfaces). This feature uses information about the operational state of the link to initiate a failure in the link that connects the edge device. This process of converting the indirect failure to a direct failure triggers a faster recovery process towards redundant links. When enabled, the port tracking feature brings down the configured links based on the failed link and forces the traffic to be redirected to another redundant link.

This chapter includes the following sections:

Information About Port Tracking

Configuring Port Tracking

Displaying Port Tracking Information

Default Port Tracking Settings

Information About Port Tracking

Generally, hosts can instantly recover from a link failure on a link that is immediately (direct link) connected to a switch. However, recovering from an indirect link failure between switches in a WAN or MAN fabric with a keepalive mechanism is dependent on several factors such as the timeout values (TOVs) and on registered state change notification (RSCN) information (see the "Fibre Channel Timeout Values" section and "About RSCN Information" section).

In Figure 48-1, when the direct link 1 to the host fails, recovery can be immediate. However, when the ISL 2 fails between the two switches, recovery depends on TOVs, RSCNs, and other factors.

Figure 48-1 Traffic Recovery Using Port Tracking

The port tracking feature monitors and detects failures that cause topology changes and brings down the links connecting the attached devices. When you enable this feature and explicitly configure the linked and tracked ports, the switch software monitors the tracked ports and alters the operational state of the linked ports on detecting a link state change.

The following terms are used in this chapter:

Tracked ports—A port whose operational state is continuously monitored. The operational state of the tracked port is used to alter the operational state of one or more ports. Fibre Channel, VSAN, SAN port channel, or a Gigabit Ethernet port can be tracked. Generally, ports in E and TE port modes can also be F ports.

Linked ports—A port whose operational state is altered based on the operational state of the tracked ports. Only physical Fibre Channel ports can be linked ports.

Port tracking has the following features:

The application brings the linked port down when the tracked port goes down. When the tracked port recovers from the failure and comes back up again, the linked port is also brought up automatically (unless otherwise configured).

You can forcefully continue to keep the linked port down, even though the tracked port comes back up. In this case, you must explicitly bring up the linked port when required.

Configuring Port Tracking

Before configuring port tracking, consider the following guidelines:

Verify that the tracked ports and the linked ports are on the same Cisco switch.

Be aware that the linked port is automatically brought down when the tracked port goes down.

Do not track a linked port back to itself (for example, Port fc2/2 to Port fc2/4 and back to Port fc2/2) to avoid recursive dependency.

This section includes the following topics:

Enabling Port Tracking

About Configuring Linked Ports

Operationally Binding a Tracked Port

About Tracking Multiple Ports

Tracking Multiple Ports

About Monitoring Ports in a VSAN

Monitoring Ports in a VSAN

About Forceful Shutdown

Forcefully Shutting Down a Tracked Port

Enabling Port Tracking

The port tracking feature is disabled by default in Cisco Nexus 5000 Series switches. When you enable this feature, port tracking is globally enabled for the entire switch.

To configure port tracking, enable the port tracking feature and configure the linked ports for the tracked port.

To enable port tracking, perform this task:

 
Command
Purpose

Step 1 

switch# configuration terminal

Enters configuration mode.

Step 2 

switch(config)# port-track enable

Enables port tracking.

switch(config)# no port-track enable

Removes the currently applied port tracking configuration and disables port tracking.

About Configuring Linked Ports

You can link ports using one of two methods:

Operationally binding the linked ports to the tracked port (default).

Continuing to keep the linked port down forcefully, even if the tracked port has recovered from the link failure.

Operationally Binding a Tracked Port

When you configure the first tracked port, operational binding is automatically in effect. When you use this method, you have the option to monitor multiple ports or monitor ports in one VSAN.

To operationally bind a tracked port, perform this task:

 
Command
Purpose

Step 1 

switch# configuration terminal

Enters configuration mode.

Step 2 

switch(config)# interface fc slot/port

Enters the interface configuration mode for the linked port. You can now configure the tracked ports.

Note This link symbolizes the direct link (1) in Figure 48-1.

Step 3 

switch(config-if)# port-track interface fc slot/port | san-port-channel port

Specifies the tracked port. When the tracked port goes down, the linked port is also brought down.

Note This link symbolizes the ISL (2) in Figure 48-1.

switch(config-if)# no port-track interface fc slot/port | san-port-channel port

Removes the port tracking configuration that is currently applied to the interface.

The following example shows how to enable port tracking for specific interfaces:

switch# configure
switch(config)# interface fc 2/4
switch(config-if)# port-track interface san-port-channel 2

About Tracking Multiple Ports

You can control the operational state of the linked port based on the operational states of multiple tracked ports. When more than one tracked port is associated with a linked port, the operational state of the linked port will be set to down only if all the associated tracked ports are down. Even if one tracked port is up, the linked port will stay up.

In Figure 48-2, only if both ISLs 2 and 3 fail, will the direct link 1 be brought down. Direct link 1 will not be brought down if either 2 or 3 are still functioning as desired.

Figure 48-2 Traffic Recovery Using Port Tracking

Tracking Multiple Ports

To track multiple ports, perform this task:

 
Command
Purpose

Step 1 

switch# configuration terminal

Enters configuration mode.

Step 2 

switch(config)# interface fc slot/port

Configures the specified interface and enters the interface configuration mode. You can now configure tracked ports.

Note This link symbolizes the direct link (1) in Figure 48-2.

Step 3 

switch(config-if)# port-track interface interface fc slot/port | san-port-channel port

Tracks the linked port with the specified interface. When the tracked port goes down, the linked port is also brought down.

Note This link symbolizes the ISL (2) in Figure 48-2.

The following example shows how to enable port tracking for multiple interfaces:

switch# configure
switch(config)# interface fc 2/3
switch(config-if)# port-track interface fc 2/3
switch(config-if)# port-track interface san-port-channel 2

About Monitoring Ports in a VSAN

You can optionally configure one VSAN from the set of all operational VSANs on the tracked port with the linked port by specifying the required VSAN. This level of flexibility provides higher granularity in tracked ports. In some cases, when a tracked port is a TE port, the set of operational VSANs on the port can change dynamically without bringing down the operational state of the port. In such cases, the port VSAN of the linked port can be monitored on the set of operational VSANs on the tracked port.

If you configure this feature, the linked port is up only when the VSAN is up on the tracked port.


Tip The specified VSAN does not have to be the same as the port VSAN of the linked port.


Monitoring Ports in a VSAN

To monitor a tracked port in a specific VSAN, perform this task

 
Command
Purpose

Step 1 

switch# configuration terminal

Enters configuration mode.

Step 2 

switch(config)# interface fc slot/port

Configures the specified interface and enters the interface configuration mode. You can now configure tracked ports.

Step 3 

switch(config-if)# port-track interface san-port-channel 1 vsan 2

Enables tracking of the SAN port channel in VSAN 2.

switch(config-if)# no port-track interface san-port-channel 1 vsan 2

Removes the VSAN association for the linked port. The SAN port channel link remains in effect.

:

About Forceful Shutdown

If a tracked port flaps frequently, then tracking ports using the operational binding feature may cause frequent topology change. In this case, you may choose to keep the port in the down state until you are able to resolve the reason for these frequent flaps. Keeping the flapping port in the down state forces the traffic to flow through the redundant path until the primary tracked port problems are resolved. When the problems are resolved and the tracked port is back up, you can explicitly enable the interface.


Tip If you configure this feature, the linked port continues to remain in the shutdown state even after the tracked port comes back up. You must explicitly remove the forced shut state (by administratively bringing up this interface) of the linked port once the tracked port is up and stable.


Forcefully Shutting Down a Tracked Port

To forcefully shut down a tracked port, perform this task:

 
Command
Purpose

Step 1 

switch# configuration terminal

Enters configuration mode.

Step 2 

switch(config)# interface fc slot/port

Configures the specified interface and enters the interface configuration mode. You can now configure tracked ports.

Step 3 

switch(config-if)# port-track force-shut

Forcefully shuts down the tracked port.

switch(config-if)# no port-track force-shut

Removes the port shutdown configuration for the tracked port.

Displaying Port Tracking Information

The show commands display the current port tracking settings for the switch.

The following example shows how to display tracked port configuration for a specific interface:

switch# show interface fc2/1
fc2/1 is down (Administratively down)
    Hardware is Fibre Channel, FCOT is short wave laser w/o OFC (SN)
    Port WWN is 20:01:00:05:30:00:0d:de
    Admin port mode is FX
    Port vsan is 1
    Receive data field Size is 2112
    Beacon is turned off
    Port tracked with interface fc2/2 (down)
    Port tracked with interface san-port-channel 1 vsan 2 (down)
5 minutes input rate 0 bits/sec, 0 bytes/sec, 0 frames/sec
...
 
   

The following example shows how to display tracked port configuration for a SAN port channel:

switch# show interface san-port-channel 1
port-channel 1 is down (No operational members)
    Hardware is Fibre Channel
    Port WWN is 24:01:00:05:30:00:0d:de
    Admin port mode is auto, trunk mode is on
    Port vsan is 2
    Linked to 1 port(s)
      Port linked to interface fc2/1
...
 
   

The following example shows how to display the port track mode:

switch# show interface fc 2/4
 
   
fc2/4 is up
    Hardware is Fibre Channel, FCOT is short wave laser
...
    Transmit B2B Credit is 64
    Receive B2B Credit is 16
    Receive data field Size is 2112
    Beacon is turned off
    Port track mode is force_shut <--this port remains shut even if the tracked port is back up
 
   

Default Port Tracking Settings

Table 48-1 lists the default settings for port tracking parameters.

Table 48-1 Default Port Tracking Parameters 

Parameters
Default

Port tracking

Disabled

Operational binding

Enabled along with port tracking