The Cisco NX-OS release that is running on a managed device may not support all the features or settings described in this chapter. For the latest feature information and caveats, see the documentation and release notes for your platform and software release.
This chapter describes how to configure link-state tracking on the Cisco Nexus 4000 Series device.
Link-state tracking is applicable only for the Cisco Nexus 4000 Series platform, beginning with the DCNM 4.2(3) release.
Link-state tracking, also known as trunk failover, is a feature that binds the link state of multiple interfaces to create redundancy in the network. The feature provides redundancy in the network when used with server network interface card (NIC) adapter teaming. When the server network adapters are configured in a primary or secondary relationship known as teaming and the link is lost on the primary interface, connectivity transparently changes to the secondary interface.
The following figure shows a network configured with link-state tracking. After you enable link-state tracking and create a link-state group, you assign interfaces to the link-state group. Interfaces connected to servers are referred to as downstream interfaces, and interfaces connected to distribution switches and network devices are referred to as upstream interfaces.
When link-state tracking is enabled, the downstream interfaces are bound to the upstream interfaces. After a set of downstream ports are associated to a set of upstream ports, if all of the upstream ports become unavailable, link-state tracking automatically puts the associated downstream ports in an error-disabled state, which causes the primary interface of the server to fail over to the secondary interface.
The configuration in the preceding figure ensures that when server NIC adapter teaming is used, the traffic flow continues uninterrupted when the uplink connection to a distribution switch is lost. The configuration is as follows:
The blade switches in the enclosure are connected to switch 1 and switch 2 through different switches.
Link-state group 1 is the primary link from all the blade servers in the enclosure (blade server 1 through blade server n) to switch 1.
Link-state group 2 is the secondary (backup) link from all the blade servers to switch 2.
In a link-state group, the upstream ports can become unavailable or lose connectivity because the switch or router fails, the cables are disconnected, or the link is lost. These interactions occur between the downstream and upstream interfaces when link-state tracking is enabled:
If any of the upstream interfaces are in the link-up state, the downstream interfaces can change to or remain in the link-up state.
If the server detects that the primary link is down, it redirects the traffic to the secondary (backup) link and the secondary link becomes the primary link.
As an example of a connectivity change from link-state group 1 to link-state group 2, when the primary link from blade switch 1 to switch 1 is lost, blade server 1 connects through its secondary Ethernet server interface to blade switch 2 in link-state group 2.
When link-state tracking is disabled, the entire feature is disabled. All the configuration for link-state tracking is removed. The downstream ports revert back to the state when no link-state tracking was set.
You can recover a downstream interface link-down condition by removing the failed downstream port from the link-state group. To recover for multiple downstream interfaces, disable the link-state group.
Licensing Requirements for Link-State Tracking
The following table shows the licensing requirements for this feature:
Link-state tracking requires no license. Any feature not included in a license package is bundled with the Cisco DCNM and is provided at no charge to you.
Link-state tracking requires an Enterprise Services license. For a complete explanation of the Cisco NX-OS licensing scheme and how to obtain and apply licenses, see the Cisco Nexus 7000 Series NX-OS Licensing Guide, Release 4.2.
Prerequisites for Link-State Tracking
Link-state tracking requires that you configure the logging level in any switch that is used for this feature. The proper logging level ensures that DCNM is synchronized with the link-state tracking status.
To set the proper logging level, enter the following commands:
logging logfile messages 6
logging level lstsvc 4
The logging level lstsvc 4 command can only be used after link-state tracking has been enabled in the switch. Whenever you enable link-state tracking, you must configure these logging-level commands to ensure that DCNM is in sync with the switch for link-state tracking management.
Guidelines and Limitations for Link-State Tracking
Link-state tracking has the following guidelines and limitations:
Ethernet 1/1–14 are the designated downstream interfaces.
Ethernet 1/15–20 are the designated up stream interfaces.
The Cisco Nexus 4000 Series switch module allows a user to configure a downstream interface as an upstream interface or an upstream interface as a downstream interface. Even though this configuration is allowed in the switch, it is not a valid configuration.
Any attempt to configure an upstream interface as downstream, or a downstream interface as upstream, generates an exception and DCNM displays a warning message. However, DCNM does not prevent a user from proceeding with the incorrect configuration.
Configuring Link-State Tracking
You can access Link-State Tracking from the Switching feature selection. Figure 2-2 shows how to configure link-state tracking.
You can remove ports that have been assigned to an upstream or downstream interface in a link-state group.
Before You Begin
Ensure that you have enabled the link-state tracking feature, created at least one link-state group, and assigned interfaces to the group.
From the Feature Selector pane, choose Switching > Link-State Tracking.
In the Summary pane, click a link-state group to highlight it.
The upstream and downstream interfaces that have been assigned to this link-state group appear.
In the Details pane, click one of the ports in the Upstream Interfaces or Downstream Interfaces table and press Delete. If you want to choose more than one port, press and hold Shift or Ctrl when you click.
You can export details about link-state groups to an Excel file (.xls). The information displays in the Excel file similar to the arrangement in the Summary pane, showing the link-state group names, upstream and downstream interfaces, and events.
From the Feature Selector pane, choose Switching > Link-State Tracking.
The available devices appear in the Summary pane.
Above the Summary pane, click the green arrow.
The Export to Excel dialog box displays.
Navigate to the location where you want to save the file.
Enter a name for the file and click Save.
The file is saved to the specified location.
Field Descriptions for Link-State Tracking
This section includes the following field descriptions for tunnel interfaces:
Link-State Summary Pane
All fields described in the following table are display only.
Table 1 Summary Pane
Names of devices and the link-state groups within them.
Subdivided into Upstream and Downstream and lists the specific interfaces assigned to this link-state group.
Status of whether the upstream switch is up or down. The upstream status is up if at least one upstream interface in that link-state group is up. When all the upstream interfaces in that group are down, this status is down.
DCNM displays a bell icon in the Event column when an event occurs, such as all upstream interfaces in the group going down. If the icon appears, you can click the Event tab to get more details about the event.
Link-State Group: Details Tab
All fields described in the following tables are display only.