Cisco Nexus 4001I and 4005I Switch Module for IBM BladeCenter NX-OS Configuration Guide
Configuring Link-State Tracking
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Configuring Link-State Tracking

Table Of Contents

Configuring Link-State Tracking

Understanding Link-State Tracking

Configuring Link-State Tracking

Default Link-State Tracking Configuration

Link-State Tracking Configuration Guidelines

Configuring Link-State Tracking

Displaying Link-State Tracking Status


Configuring Link-State Tracking


This chapter describes how to configure link-state tracking and includes the following sections:

Understanding Link-State Tracking

Configuring Link-State Tracking

Understanding Link-State Tracking

Link-state tracking, also known as trunk failover, is a feature that binds the link state of multiple interfaces. Link-state tracking 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.

Figure 16-1 shows a network configured with link-state tracking. To enable link-state tracking, create a link-state group, and specify the interfaces that are assigned 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. This causes the primary interface of the server to failover to the secondary interface.

Figure 16-1 Typical Link-State Tracking Configuration

The configuration in Figure 16-1 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 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 are the interactions 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 are reverted 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.

Configuring Link-State Tracking

The following section describes how to configure link-state tracking ports and includes the following topics:

Default Link-State Tracking Configuration

Link-State Tracking Configuration Guidelines

Configuring Link-State Tracking

Displaying Link-State Tracking Status

Default Link-State Tracking Configuration

The link-state tracking feature is disabled. No link-state groups are defined.

Link-State Tracking Configuration Guidelines

Follow the listed guidelines when configuring link-state tracking:

An interface that is defined as an upstream interface cannot also be defined as a downstream interface in the same or a different link-state group. The reverse is also true.

An interface cannot be a member of more than one link-state group.

Management interfaces cannot be members of a link-state group.

An EtherChannel can be configured as upstream member in a link-state group. However, do not configure it as a downstream member.

Only interfaces ethernet 1/1 through 1/14 can be configured as downstream ports in a specific link-state group.

Only interfaces ethernet 1/15 through 1/20 can be configured as upstream ports in a specific link-state group.

Configuring Link-State Tracking

Beginning in privileged EXEC mode, and to configure a link-state group and to assign an interface to a group, perform this task:

 
Command
Purpose

Step 1 

configure terminal

Enters global configuration mode.

Step 1 

feature lst

Enables link-state track feature.

Step 2 

link state track number

Creates a link-state group, and enable link-state tracking. The group number can be 1 to 6. The default is 1.

Step 3 

interface interface-id

Specifies a physical interface or range of interfaces to configure, and enters interface configuration mode.

Valid interfaces include switch ports in access or trunk mode (IEEE 802.1q), routed ports, or multiple ports bundled into an EtherChannel interface (static or LACP), that is also in trunk mode.

Step 4 

link state group [number] {upstream | downstream}

Specifies a link-state group, and configures the interface as either an upstream or downstream interface in the group. The group number can be 1 to 6. The default is 1.

Step 5 

end

Returns to privileged EXEC mode.

Step 6 

show running-config

Verifies your entries.

Step 7 

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

The following example shows how to create a link-state group and to configure the interface:

switch# configure terminal 
switch(config)# feature lst 
switch(config)# link state track 1
switch(config)# interface port-channel 1
switch(config-if)# link state group 1 upstream
switch(config-if)# end
 
   

The following example shows how to remove an interface from a link-state group:

switch# configure terminal 
switch(config)# interface port-channel 1
switch(config-if)# no link state group 1 upstream
switch(config-if)# end
 
   

To disable the link state track feature, use the no feature lst command.

The link-state group cannot be disabled.

Displaying Link-State Tracking Status

Use the show link state group command to display the link-state group information. Enter this command without keywords to display information about all link-state groups. Enter the group number to display information specific to the group. Enter the detail keyword to display detailed information about the group.

The following is sample output from the show link state group 1 command:

switch> show link state group 1
Link State Group: 1      Status: Enabled, Down
 
   

The following is sample output from the show link state group detail command:

switch> show link state group detail
(Up):Interface up   (Dwn):Interface Down   (Dis):Interface disabled
Link State Group: 1      Status: Enabled, Up
Upstream Interfaces   : Po1(Up)
Downstream Interfaces : Gi0/3(Up) Gi0/4(Up)
(Up):Interface up   (Dwn):Interface Down   (Dis):Interface disabled