Software Configuration Guide, Cisco IOS Release 15.2(2)E (Catalyst 2960, 2960-S, 2960-SF and 2960-Plus Switches)
Configuring Link-State Tracking
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Configuring Link-State Tracking

Configuring Link-State Tracking

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

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Restrictions for Configuring Link-State Tracking

  • You can configure only two link-state groups per switch.
  • An interface cannot be a member of more than one link-state group.
  • An interface that is defined as an upstream interface in a link-state group cannot also be defined as a downstream interface in the link-state group.
  • Do not enable link-state tracking on individual interfaces that will part of a downstream EtherChannel interface.

Understanding Link-State Tracking

Link-state tracking, also known as trunk failover, binds the link state of multiple interfaces. Link-state tracking can be with server NIC adapter teaming to provide redundancy in the network. When the server NIC adapters are configured in a primary or secondary relationship, and the link is lost on the primary interface, network connectivity is transparently changed to the secondary interface.

To enable link-state tracking, create a link-state group, and specify the interfaces that are assigned to the link-state group. An interface can be an aggregation of ports (an EtherChannel), a single physical port in access or trunk mode, or a routed port. In a link-state group, these interfaces are bundled together. The downstream interfaces are bound to the upstream interfaces. 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.


Note


An interface can be an aggregation of ports (an EtherChannel) or a single physical port in either access or trunk mode .


The configuration in this figure ensures that the network traffic flow is balanced.

Figure 1. Typical Link-State Tracking Configuration



  • For links to switches and other network devices
    • Server 1 and server 2 use switch A for primary links and switch B for secondary links.
    • Server 3 and server 4 use switch B for primary links and switch A for secondary links.
  • Link-state group 1 on switch A
    • Switch A provides primary links to server 1 and server 2 through link-state group 1. Port 1 is connected to server 1, and port 2 is connected to server 2. Port 1 and port 2 are the downstream interfaces in link-state group 1.
    • Port 5 and port 6 are connected to distribution switch 1 through link-state group 1. Port 5 and port 6 are the upstream interfaces in link-state group 1.
  • Link-state group 2 on switch A
    • Switch A provides secondary links to server 3 and server 4 through link-state group 2. Port 3 is connected to server 3, and port 4 is connected to server 4. Port 3 and port 4 are the downstream interfaces in link-state group 2.
    • Port 7 and port 8 are connected to distribution switch 2 through link-state group 2. Port 7 and port 8 are the upstream interfaces in link-state group 2.
  • Link-state group 2 on switch B
    • Switch B provides primary links to server 3 and server 4 through link-state group 2. Port 3 is connected to server 3, and port 4 is connected to server 4. Port 3 and port 4 are the downstream interfaces in link-state group 2.
    • Port 5 and port 6 are connected to distribution switch 2 through link-state group 2. Port 5 and port 6 are the upstream interfaces in link-state group 2.
  • Link-state group 1 on switch B
    • Switch B provides secondary links to server 1 and server 2 through link-state group 1. Port 1 is connected to server 1, and port 2 is connected to server 2. Port 1 and port 2 are the downstream interfaces in link-state group 1.
    • Port 7 and port 8 are connected to distribution switch 1 through link-state group 1. Port 7 and port 8 are the upstream interfaces in link-state group 1.

In a link-state group, the upstream ports can become unavailable or lose connectivity because the distribution 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 all of the upstream interfaces become unavailable, link-state tracking automatically puts the downstream interfaces in the error-disabled state. Connectivity to and from the servers is automatically changed from the primary server interface to the secondary server interface. For example, in the previous figure, if the upstream link for port 6 is lost, the link states of downstream ports 1 and 2 do not change. However, if the link for upstream port 5 is also lost, the link state of the downstream ports changes to the link-down state. Connectivity to server 1 and server 2 is then changed from link-state group1 to link-state group 2. The downstream ports 3 and 4 do not change state because they are in link-group 2.
  • If the link-state group is configured, link-state tracking is disabled, and the upstream interfaces lose connectivity, the link states of the downstream interfaces remain unchanged. The server does not recognize that upstream connectivity has been lost and does not failover to the secondary interface.

You can recover a downstream interface link-down condition by removing the failed downstream port from the link-state group. To recover multiple downstream interfaces, disable the link-state group.

How to Configure Link-State Tracking

To enable link-state tracking, create a link-state group and specify the interfaces that are assigned to the group. This task is optional.

SUMMARY STEPS

    1.    configure terminal

    2.    link state track number

    3.    interface interface-id

    4.    link state group number{upstream | downstream}

    5.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1configure terminal


    Example:
    Switch# configure terminal
    
    
     

    Enters global configuration mode.

     
    Step 2link state track number


    Example:
    Switch(config)# link state track 2
    
    
     

    Creates a link-state group and enables link-state tracking. The group number can be 1 or 2; the default is 1.

     
    Step 3 interface interface-id


    Example:
    Switch(config)# interface gigabitethernet2/0/1
    
    
     

    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, routed ports, and multiple ports bundled into an EtherChannel interface (static, PAgP, or LACP) in trunk mode.

    Note   

    Do not enable link-state tracking on individual interfaces that will be part of a downstream EtherChannel interface.

     
    Step 4 link state group number{upstream | downstream}


    Example:
    Switch(config-if)# link state group 2 upstream
    
    
     

    Specifies a link-state group and configures the interface as either an upstream or downstream interface in the group.

     
    Step 5end


    Example:
    Switch(config-if)# end
    
    
     

    Returns to privileged EXEC mode.

     

    Monitoring Link-State Tracking

    You can display link-state tracking status using the command in this table.

    Table 1 Commands for Monitoring Link-State Tracking Status

    Command

    Description

    show link state group number detail

    Displays the link-state group information.

    Configuring Link-State Tracking: Example

    This example shows how to create the link-state group 1 and configure the interfaces in the link-state group.

    		Switch# configure terminal
    		Switch(config)# link state track 1
    		Switch(config-if)# interface range gigabitethernet1/0/21-22 
    		Switch(config-if)# link state group 1 upstream
    		Switch(config-if)# interface gigabitethernet1/0/1
    		Switch(config-if)# link state group 1 downstream
    		Switch(config-if)# interface gigabitethernet1/0/3
    		Switch(config-if)# link state group 1 downstream
    		Switch(config-if)# interface gigabitethernet1/0/5
      Switch(config-if)# link state group 1 downstream 
      Switch(config-if)# end